diff --git a/docs/about.html b/docs/about.html index 5cdc41d1d..bc3d84ba0 100644 --- a/docs/about.html +++ b/docs/about.html @@ -115,7 +115,7 @@ license.
Logos made by Angelos Chalaris and ribbon made by Tim Holman are licensed under the MIT license.
Sponsored by DigitalOcean

+ width="20px" height="20px" alt="DigitalOcean">DigitalOcean


About    Contributing    Archive    Glossary

diff --git a/docs/adapter.html b/docs/adapter.html index 0ff2e5edd..4e2d75069 100644 --- a/docs/adapter.html +++ b/docs/adapter.html @@ -73,10 +73,10 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Adapter

intermediate

ary

Creates a function that accepts up to n arguments, ignoring any additional arguments.

Call the provided function, fn, with up to n arguments, using Array.slice(0,n) and the spread operator (...).

const ary = (fn, n) => (...args) => fn(...args.slice(0, n));
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Adapter
ary
Creates a function that accepts up to n arguments, ignoring any additional arguments.
Call the provided function, fn, with up to n arguments, using Array.slice(0,n) and the spread operator (...).
const ary = (fn, n) => (...args) => fn(...args.slice(0, n));
 
const firstTwoMax = ary(Math.max, 2);
 [[2, 6, 'a'], [8, 4, 6], [10]].map(x => firstTwoMax(...x)); // [6, 8, 10]
-
intermediate
call
Given a key and a set of arguments, call them when given a context. Primarily useful in composition.
Use a closure to call a stored key with stored arguments.
const call = (key, ...args) => context => context[key](...args);
+
call
Given a key and a set of arguments, call them when given a context. Primarily useful in composition.
Use a closure to call a stored key with stored arguments.
const call = (key, ...args) => context => context[key](...args);
 
Promise.resolve([1, 2, 3])
   .then(call('map', x => 2 * x))
   .then(console.log); //[ 2, 4, 6 ]
@@ -84,13 +84,13 @@
 Promise.resolve([1, 2, 3])
   .then(map(x => 2 * x))
   .then(console.log); //[ 2, 4, 6 ]
-
intermediate
collectInto
Changes a function that accepts an array into a variadic function.
Given a function, return a closure that collects all inputs into an array-accepting function.
const collectInto = fn => (...args) => fn(args);
+
collectInto
Changes a function that accepts an array into a variadic function.
Given a function, return a closure that collects all inputs into an array-accepting function.
const collectInto = fn => (...args) => fn(args);
 
const Pall = collectInto(Promise.all.bind(Promise));
 let p1 = Promise.resolve(1);
 let p2 = Promise.resolve(2);
 let p3 = new Promise(resolve => setTimeout(resolve, 2000, 3));
 Pall(p1, p2, p3).then(console.log); // [1, 2, 3] (after about 2 seconds)
-
intermediate
flip
Flip takes a function as an argument, then makes the first argument the last.
Return a closure that takes variadic inputs, and splices the last argument to make it the first argument before applying the rest.
const flip = fn => (first, ...rest) => fn(...rest, first);
+
flip
Flip takes a function as an argument, then makes the first argument the last.
Return a closure that takes variadic inputs, and splices the last argument to make it the first argument before applying the rest.
const flip = fn => (first, ...rest) => fn(...rest, first);
 
let a = { name: 'John Smith' };
 let b = {};
 const mergeFrom = flip(Object.assign);
@@ -98,15 +98,15 @@ Promise.reso
 mergePerson(b); // == b
 b = {};
 Object.assign(b, a); // == b
-
intermediate
over
Creates a function that invokes each provided function with the arguments it receives and returns the results.
Use Array.map() and Function.apply() to apply each function to the given arguments.
const over = (...fns) => (...args) => fns.map(fn => fn.apply(null, args));
+
over
Creates a function that invokes each provided function with the arguments it receives and returns the results.
Use Array.map() and Function.apply() to apply each function to the given arguments.
const over = (...fns) => (...args) => fns.map(fn => fn.apply(null, args));
 
const minMax = over(Math.min, Math.max);
 minMax(1, 2, 3, 4, 5); // [1,5]
-
intermediate
overArgs
Creates a function that invokes the provided function with its arguments transformed.
Use Array.map() to apply transforms to args in combination with the spread operator (...) to pass the transformed arguments to fn.
const overArgs = (fn, transforms) => (...args) => fn(...args.map((val, i) => transforms[i](val)));
+
overArgs
Creates a function that invokes the provided function with its arguments transformed.
Use Array.map() to apply transforms to args in combination with the spread operator (...) to pass the transformed arguments to fn.
const overArgs = (fn, transforms) => (...args) => fn(...args.map((val, i) => transforms[i](val)));
 
const square = n => n * n;
 const double = n => n * 2;
 const fn = overArgs((x, y) => [x, y], [square, double]);
 fn(9, 3); // [81, 6]
-
intermediate
pipeAsyncFunctions
Performs left-to-right function composition for asynchronous functions.
Use Array.reduce() with the spread operator (...) to perform left-to-right function composition using Promise.then(). The functions can return a combination of: simple values, Promise's, or they can be defined as async ones returning through await. All functions must be unary.
const pipeAsyncFunctions = (...fns) => arg => fns.reduce((p, f) => p.then(f), Promise.resolve(arg));
+
pipeAsyncFunctions
Performs left-to-right function composition for asynchronous functions.
Use Array.reduce() with the spread operator (...) to perform left-to-right function composition using Promise.then(). The functions can return a combination of: simple values, Promise's, or they can be defined as async ones returning through await. All functions must be unary.
const pipeAsyncFunctions = (...fns) => arg => fns.reduce((p, f) => p.then(f), Promise.resolve(arg));
 
const sum = pipeAsyncFunctions(
   x => x + 1,
   x => new Promise(resolve => setTimeout(() => resolve(x + 2), 1000)),
@@ -116,18 +116,18 @@ Object.assig
 (async () => {
   console.log(await sum(5)); // 15 (after one second)
 })();
-
intermediate
pipeFunctions
Performs left-to-right function composition.
Use Array.reduce() with the spread operator (...) to perform left-to-right function composition. The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
const pipeFunctions = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)));
+
pipeFunctions
Performs left-to-right function composition.
Use Array.reduce() with the spread operator (...) to perform left-to-right function composition. The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
const pipeFunctions = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)));
 
const add5 = x => x + 5;
 const multiply = (x, y) => x * y;
 const multiplyAndAdd5 = pipeFunctions(multiply, add5);
 multiplyAndAdd5(5, 2); // 15
-
intermediate
promisify
Converts an asynchronous function to return a promise.
Use currying to return a function returning a Promise that calls the original function. Use the ...rest operator to pass in all the parameters.
In Node 8+, you can use util.promisify
const promisify = func => (...args) =>
+
promisify
Converts an asynchronous function to return a promise.
Use currying to return a function returning a Promise that calls the original function. Use the ...rest operator to pass in all the parameters.
In Node 8+, you can use util.promisify
const promisify = func => (...args) =>
   new Promise((resolve, reject) =>
     func(...args, (err, result) => (err ? reject(err) : resolve(result)))
   );
 
const delay = promisify((d, cb) => setTimeout(cb, d));
 delay(2000).then(() => console.log('Hi!')); // // Promise resolves after 2s
-
intermediate
rearg
Creates a function that invokes the provided function with its arguments arranged according to the specified indexes.
Use Array.map() to reorder arguments based on indexes in combination with the spread operator (...) to pass the transformed arguments to fn.
const rearg = (fn, indexes) => (...args) => fn(...indexes.map(i => args[i]));
+
rearg
Creates a function that invokes the provided function with its arguments arranged according to the specified indexes.
Use Array.map() to reorder arguments based on indexes in combination with the spread operator (...) to pass the transformed arguments to fn.
const rearg = (fn, indexes) => (...args) => fn(...indexes.map(i => args[i]));
 
var rearged = rearg(
   function(a, b, c) {
     return [a, b, c];
@@ -135,9 +135,9 @@ Object.assig
   [2, 0, 1]
 );
 rearged('b', 'c', 'a'); // ['a', 'b', 'c']
-
intermediate
spreadOver
Takes a variadic function and returns a closure that accepts an array of arguments to map to the inputs of the function.
Use closures and the spread operator (...) to map the array of arguments to the inputs of the function.
const spreadOver = fn => argsArr => fn(...argsArr);
+
spreadOver
Takes a variadic function and returns a closure that accepts an array of arguments to map to the inputs of the function.
Use closures and the spread operator (...) to map the array of arguments to the inputs of the function.
const spreadOver = fn => argsArr => fn(...argsArr);
 
const arrayMax = spreadOver(Math.max);
 arrayMax([1, 2, 3]); // 3
-
intermediate
unary
Creates a function that accepts up to one argument, ignoring any additional arguments.
Call the provided function, fn, with just the first argument given.
const unary = fn => val => fn(val);
+
unary
Creates a function that accepts up to one argument, ignoring any additional arguments.
Call the provided function, fn, with just the first argument given.
const unary = fn => val => fn(val);
 
['6', '8', '10'].map(unary(parseInt)); // [6, 8, 10]
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/archive.html b/docs/archive.html index 2bc88dffc..927e446bc 100644 --- a/docs/archive.html +++ b/docs/archive.html @@ -73,7 +73,7 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Snippets Archive

These snippets, while useful and interesting, didn't quite make it into the repository due to either having very specific use-cases or being outdated. However we felt like they might still be useful to some readers, so here they are.


binarySearch

Use recursion. Similar to Array.indexOf() that finds the index of a value within an array. The difference being this operation only works with sorted arrays which offers a major performance boost due to it's logarithmic nature when compared to a linear search or Array.indexOf().

Search a sorted array by repeatedly dividing the search interval in half. Begin with an interval covering the whole array. If the value of the search is less than the item in the middle of the interval, recurse into the lower half. Otherwise recurse into the upper half. Repeatedly recurse until the value is found which is the mid or you've recursed to a point that is greater than the length which means the value doesn't exist and return -1.

const binarySearch = (arr, val, start = 0, end = arr.length - 1) => {
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Snippets Archive
These snippets, while useful and interesting, didn't quite make it into the repository due to either having very specific use-cases or being outdated. However we felt like they might still be useful to some readers, so here they are.

binarySearch
Use recursion. Similar to Array.indexOf() that finds the index of a value within an array. The difference being this operation only works with sorted arrays which offers a major performance boost due to it's logarithmic nature when compared to a linear search or Array.indexOf().
Search a sorted array by repeatedly dividing the search interval in half. Begin with an interval covering the whole array. If the value of the search is less than the item in the middle of the interval, recurse into the lower half. Otherwise recurse into the upper half. Repeatedly recurse until the value is found which is the mid or you've recursed to a point that is greater than the length which means the value doesn't exist and return -1.
const binarySearch = (arr, val, start = 0, end = arr.length - 1) => {
   if (start > end) return -1;
   const mid = Math.floor((start + end) / 2);
   if (arr[mid] > val) return binarySearch(arr, val, start, mid - 1);
@@ -82,7 +82,7 @@
 };
 
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 6); // 2
 binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 21); // -1
-
cleanObj
Removes any properties except the ones specified from a JSON object.
Use Object.keys() method to loop over given JSON object and deleting keys that are not included in given array. If you pass a special key,childIndicator, it will search deeply apply the function to inner objects, too.
const cleanObj = (obj, keysToKeep = [], childIndicator) => {
+
cleanObj
Removes any properties except the ones specified from a JSON object.
Use Object.keys() method to loop over given JSON object and deleting keys that are not included in given array. If you pass a special key,childIndicator, it will search deeply apply the function to inner objects, too.
const cleanObj = (obj, keysToKeep = [], childIndicator) => {
   Object.keys(obj).forEach(key => {
     if (key === childIndicator) {
       cleanObj(obj[key], keysToKeep, childIndicator);
@@ -94,12 +94,12 @@
 };
 
const testObj = { a: 1, b: 2, children: { a: 1, b: 2 } };
 cleanObj(testObj, ['a'], 'children'); // { a: 1, children : { a: 1}}
-
collatz
Applies the Collatz algorithm.
If n is even, return n/2. Otherwise, return 3n+1.
const collatz = n => (n % 2 === 0 ? n / 2 : 3 * n + 1);
+
collatz
Applies the Collatz algorithm.
If n is even, return n/2. Otherwise, return 3n+1.
const collatz = n => (n % 2 === 0 ? n / 2 : 3 * n + 1);
 
collatz(8); // 4
-
countVowels
Retuns number of vowels in provided string.
Use a regular expression to count the number of vowels (A, E, I, O, U) in a string.
const countVowels = str => (str.match(/[aeiou]/gi) || []).length;
+
countVowels
Retuns number of vowels in provided string.
Use a regular expression to count the number of vowels (A, E, I, O, U) in a string.
const countVowels = str => (str.match(/[aeiou]/gi) || []).length;
 
countVowels('foobar'); // 3
 countVowels('gym'); // 0
-
factors
Returns the array of factors of the given num. If the second argument is set to true returns only the prime factors of num. If num is 1 or 0 returns an empty array. If num is less than 0 returns all the factors of -int together with their additive inverses.
Use Array.from(), Array.map() and Array.filter() to find all the factors of num. If given num is negative, use Array.reduce() to add the additive inverses to the array. Return all results if primes is false, else determine and return only the prime factors using isPrime and Array.filter(). Omit the second argument, primes, to return prime and non-prime factors by default.
Note:- Negative numbers are not considered prime.
const factors = (num, primes = false) => {
+
factors
Returns the array of factors of the given num. If the second argument is set to true returns only the prime factors of num. If num is 1 or 0 returns an empty array. If num is less than 0 returns all the factors of -int together with their additive inverses.
Use Array.from(), Array.map() and Array.filter() to find all the factors of num. If given num is negative, use Array.reduce() to add the additive inverses to the array. Return all results if primes is false, else determine and return only the prime factors using isPrime and Array.filter(). Omit the second argument, primes, to return prime and non-prime factors by default.
Note:- Negative numbers are not considered prime.
const factors = (num, primes = false) => {
   const isPrime = num => {
     const boundary = Math.floor(Math.sqrt(num));
     for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
@@ -122,10 +122,10 @@
 factors(12, true); // [2,3]
 factors(-12); // [2, -2, 3, -3, 4, -4, 6, -6, 12, -12]
 factors(-12, true); // [2,3]
-
fibonacciCountUntilNum
Returns the number of fibonnacci numbers up to num(0 and num inclusive).
Use a mathematical formula to calculate the number of fibonacci numbers until num.
const fibonacciCountUntilNum = num =>
+
fibonacciCountUntilNum
Returns the number of fibonnacci numbers up to num(0 and num inclusive).
Use a mathematical formula to calculate the number of fibonacci numbers until num.
const fibonacciCountUntilNum = num =>
   Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
 
fibonacciCountUntilNum(10); // 7
-
fibonacciUntilNum
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1). Use Array.reduce() to add values into the array, using the sum of the last two values, except for the first two. Uses a mathematical formula to calculate the length of the array required.
const fibonacciUntilNum = num => {
+
fibonacciUntilNum
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1). Use Array.reduce() to add values into the array, using the sum of the last two values, except for the first two. Uses a mathematical formula to calculate the length of the array required.
const fibonacciUntilNum = num => {
   let n = Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
   return Array.from({ length: n }).reduce(
     (acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
@@ -133,7 +133,7 @@
   );
 };
 
fibonacciUntilNum(10); // [ 0, 1, 1, 2, 3, 5, 8 ]
-
howManyTimes
Returns the number of times num can be divided by divisor (integer or fractional) without getting a fractional answer. Works for both negative and positive integers.
If divisor is -1 or 1 return Infinity. If divisor is -0 or 0 return 0. Otherwise, keep dividing num with divisor and incrementing i, while the result is an integer. Return the number of times the loop was executed, i.
const howManyTimes = (num, divisor) => {
+
howManyTimes
Returns the number of times num can be divided by divisor (integer or fractional) without getting a fractional answer. Works for both negative and positive integers.
If divisor is -1 or 1 return Infinity. If divisor is -0 or 0 return 0. Otherwise, keep dividing num with divisor and incrementing i, while the result is an integer. Return the number of times the loop was executed, i.
const howManyTimes = (num, divisor) => {
   if (divisor === 1 || divisor === -1) return Infinity;
   if (divisor === 0) return 0;
   let i = 0;
@@ -147,7 +147,7 @@
 howManyTimes(100, 2.5); // 2
 howManyTimes(100, 0); // 0
 howManyTimes(100, -1); // Infinity
-
httpDelete
Makes a DELETE request to the passed URL.
Use XMLHttpRequest web api to make a delete request to the given url. Handle the onload event, by running the provided callback function. Handle the onerror event, by running the provided err function. Omit the third argument, err to log the request to the console's error stream by default.
const httpDelete = (url, callback, err = console.error) => {
+
httpDelete
Makes a DELETE request to the passed URL.
Use XMLHttpRequest web api to make a delete request to the given url. Handle the onload event, by running the provided callback function. Handle the onerror event, by running the provided err function. Omit the third argument, err to log the request to the console's error stream by default.
const httpDelete = (url, callback, err = console.error) => {
   const request = new XMLHttpRequest();
   request.open("DELETE", url, true);
   request.onload = () => callback(request);
@@ -157,7 +157,7 @@
 
httpDelete('https://website.com/users/123', request => {
   console.log(request.responseText);
 }); // 'Deletes a user from the database'
-
httpPut
Makes a PUT request to the passed URL.
Use XMLHttpRequest web api to make a put request to the given url. Set the value of an HTTP request header with setRequestHeader method. Handle the onload event, by running the provided callback function. Handle the onerror event, by running the provided err function. Omit the last argument, err to log the request to the console's error stream by default.
const httpPut = (url, data, callback, err = console.error) => {
+
httpPut
Makes a PUT request to the passed URL.
Use XMLHttpRequest web api to make a put request to the given url. Set the value of an HTTP request header with setRequestHeader method. Handle the onload event, by running the provided callback function. Handle the onerror event, by running the provided err function. Omit the last argument, err to log the request to the console's error stream by default.
const httpPut = (url, data, callback, err = console.error) => {
     const request = new XMLHttpRequest();
     request.open("PUT", url, true);
     request.setRequestHeader('Content-type','application/json; charset=utf-8');
@@ -170,24 +170,24 @@
 httpPut('https://website.com/users/123', data, request => {
   console.log(request.responseText);
 }); // 'Updates a user's password in database'
-
isArmstrongNumber
Checks if the given number is an Armstrong number or not.
Convert the given number into an array of digits. Use the exponent operator (**) to get the appropriate power for each digit and sum them up. If the sum is equal to the number itself, return true otherwise false.
const isArmstrongNumber = digits =>
+
isArmstrongNumber
Checks if the given number is an Armstrong number or not.
Convert the given number into an array of digits. Use the exponent operator (**) to get the appropriate power for each digit and sum them up. If the sum is equal to the number itself, return true otherwise false.
const isArmstrongNumber = digits =>
   (arr => arr.reduce((a, d) => a + parseInt(d) ** arr.length, 0) == digits)(
     (digits + '').split('')
   );
 
isArmstrongNumber(1634); // true
 isArmstrongNumber(56); // false
-
isSimilar
Determines if the pattern matches with str.
Use String.toLowerCase() to convert both strings to lowercase, then loop through str and determine if it contains all characters of pattern and in the correct order. Adapted from here.
const isSimilar = (pattern, str) =>
+
isSimilar
Determines if the pattern matches with str.
Use String.toLowerCase() to convert both strings to lowercase, then loop through str and determine if it contains all characters of pattern and in the correct order. Adapted from here.
const isSimilar = (pattern, str) =>
 	[...str].reduce(
 		(matchIndex, char) => char.toLowerCase() === (pattern[matchIndex]  || '').toLowerCase() ? matchIndex + 1 : matchIndex, 0
 	) === pattern.length ? true : false;
 
isSimilar('rt','Rohit'); // true
 isSimilar('tr','Rohit'); // false
-
JSONToDate
Converts a JSON object to a date.
Use Date(), to convert dates in JSON format to readable format (dd/mm/yyyy).
const JSONToDate = arr => {
+
JSONToDate
Converts a JSON object to a date.
Use Date(), to convert dates in JSON format to readable format (dd/mm/yyyy).
const JSONToDate = arr => {
   const dt = new Date(parseInt(arr.toString().substr(6)));
   return `${dt.getDate()}/${dt.getMonth() + 1}/${dt.getFullYear()}`;
 };
 
JSONToDate(/Date(1489525200000)/); // "14/3/2017"
-
levenshteinDistance
Calculates the Levenshtein distance between two strings.
Calculates the number of changes (substitutions, deletions or additions) required to convert string1 to string2. Can also be used to compare two strings as shown in the second example.
const levenshteinDistance = (string1, string2) => {
+
levenshteinDistance
Calculates the Levenshtein distance between two strings.
Calculates the number of changes (substitutions, deletions or additions) required to convert string1 to string2. Can also be used to compare two strings as shown in the second example.
const levenshteinDistance = (string1, string2) => {
     if(string1.length === 0) return string2.length;
     if(string2.length === 0) return string1.length;
     let matrix = Array(string2.length + 1).fill(0).map((x,i) => [i]);
@@ -207,7 +207,7 @@
 
levenshteinDistance('30-seconds-of-code','30-seconds-of-python-code'); // 7
 const compareStrings = (string1,string2) => (100 - levenshteinDistance(string1,string2) / Math.max(string1.length,string2.length));
 compareStrings('30-seconds-of-code', '30-seconds-of-python-code'); // 99.72 (%)
-
quickSort
QuickSort an Array (ascending sort by default).
Use recursion. Use Array.filter and spread operator (...) to create an array that all elements with values less than the pivot come before the pivot, and all elements with values greater than the pivot come after it. If the parameter desc is truthy, return array sorts in descending order.
const quickSort = ([n, ...nums], desc) =>
+
quickSort
QuickSort an Array (ascending sort by default).
Use recursion. Use Array.filter and spread operator (...) to create an array that all elements with values less than the pivot come before the pivot, and all elements with values greater than the pivot come after it. If the parameter desc is truthy, return array sorts in descending order.
const quickSort = ([n, ...nums], desc) =>
   isNaN(n)
     ? []
     : [
@@ -217,10 +217,10 @@
       ];
 
quickSort([4, 1, 3, 2]); // [1,2,3,4]
 quickSort([4, 1, 3, 2], true); // [4,3,2,1]
-
removeVowels
Returns all the vowels in a str replaced by repl.
Use String.replace() with a regexp to replace all vowels in str. Omot repl to use a default value of ''.
const removeVowels = (str, repl = '') => str.replace(/[aeiou]/gi,repl);
+
removeVowels
Returns all the vowels in a str replaced by repl.
Use String.replace() with a regexp to replace all vowels in str. Omot repl to use a default value of ''.
const removeVowels = (str, repl = '') => str.replace(/[aeiou]/gi,repl);
 
removeVowels("foobAr"); // "fbr"
 removeVowels("foobAr","*"); // "f**b*r"
-
solveRPN
Solves the given mathematical expression in reverse polish notation. Throws appropriate errors if there are unrecognized symbols or the expression is wrong. The valid operators are :- +,-,*,/,^,** (^&** are the exponential symbols and are same). This snippet does not supports any unary operators.
Use a dictionary, OPERATORS to specify each operator's matching mathematical operation. Use String.replace() with a regular expression to replace ^ with **, String.split() to tokenize the string and Array.filter() to remove empty tokens. Use Array.forEach() to parse each symbol, evaluate it as a numeric value or operator and solve the mathematical expression. Numeric values are converted to floating point numbers and pushed to a stack, while operators are evaluated using the OPERATORS dictionary and pop elements from the stack to apply operations.
const solveRPN = rpn => {
+
solveRPN
Solves the given mathematical expression in reverse polish notation. Throws appropriate errors if there are unrecognized symbols or the expression is wrong. The valid operators are :- +,-,*,/,^,** (^&** are the exponential symbols and are same). This snippet does not supports any unary operators.
Use a dictionary, OPERATORS to specify each operator's matching mathematical operation. Use String.replace() with a regular expression to replace ^ with **, String.split() to tokenize the string and Array.filter() to remove empty tokens. Use Array.forEach() to parse each symbol, evaluate it as a numeric value or operator and solve the mathematical expression. Numeric values are converted to floating point numbers and pushed to a stack, while operators are evaluated using the OPERATORS dictionary and pop elements from the stack to apply operations.
const solveRPN = rpn => {
   const OPERATORS = {
     '*': (a, b) => a * b,
     '+': (a, b) => a + b,
@@ -250,10 +250,10 @@
 };
 
solveRPN('15 7 1 1 + - / 3 * 2 1 1 + + -'); // 5
 solveRPN('2 3 ^'); // 8
-
speechSynthesis
Performs speech synthesis (experimental).
Use SpeechSynthesisUtterance.voice and window.speechSynthesis.getVoices() to convert a message to speech. Use window.speechSynthesis.speak() to play the message.
Learn more about the SpeechSynthesisUtterance interface of the Web Speech API.
const speechSynthesis = message => {
+
speechSynthesis
Performs speech synthesis (experimental).
Use SpeechSynthesisUtterance.voice and window.speechSynthesis.getVoices() to convert a message to speech. Use window.speechSynthesis.speak() to play the message.
Learn more about the SpeechSynthesisUtterance interface of the Web Speech API.
const speechSynthesis = message => {
   const msg = new SpeechSynthesisUtterance(message);
   msg.voice = window.speechSynthesis.getVoices()[0];
   window.speechSynthesis.speak(msg);
 };
 
speechSynthesis('Hello, World'); // // plays the message
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/browser.html b/docs/browser.html index 6ac0ffd16..4ad922e8d 100644 --- a/docs/browser.html +++ b/docs/browser.html @@ -73,17 +73,17 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Browser

intermediate

arrayToHtmlList

Converts the given array elements into <li> tags and appends them to the list of the given id.

Use Array.map(), document.querySelector(), and an anonymous inner closure to create a list of html tags.

const arrayToHtmlList = (arr, listID) =>
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Browser
arrayToHtmlList
Converts the given array elements into <li> tags and appends them to the list of the given id.
Use Array.map(), document.querySelector(), and an anonymous inner closure to create a list of html tags.
const arrayToHtmlList = (arr, listID) =>
   (el => (
     (el = document.querySelector('#' + listID)),
     (el.innerHTML += arr.map(item => `<li>${item}</li>`).join(''))
   ))();
 
arrayToHtmlList(['item 1', 'item 2'], 'myListID');
-
intermediate
bottomVisible
Returns true if the bottom of the page is visible, false otherwise.
Use scrollY, scrollHeight and clientHeight to determine if the bottom of the page is visible.
const bottomVisible = () =>
+
bottomVisible
Returns true if the bottom of the page is visible, false otherwise.
Use scrollY, scrollHeight and clientHeight to determine if the bottom of the page is visible.
const bottomVisible = () =>
   document.documentElement.clientHeight + window.scrollY >=
   (document.documentElement.scrollHeight || document.documentElement.clientHeight);
 
bottomVisible(); // true
-
advanced
copyToClipboard
⚠️ NOTICE: The same functionality can be easily implemented by using the new asynchronous Clipboard API, which is still experimental but should be used in the future instead of this snippet. Find out more about it here.
Copy a string to the clipboard. Only works as a result of user action (i.e. inside a click event listener).
Create a new <textarea> element, fill it with the supplied data and add it to the HTML document. Use Selection.getRangeAt()to store the selected range (if any). Use document.execCommand('copy') to copy to the clipboard. Remove the <textarea> element from the HTML document. Finally, use Selection().addRange() to recover the original selected range (if any).
const copyToClipboard = str => {
+
copyToClipboard
⚠️ NOTICE: The same functionality can be easily implemented by using the new asynchronous Clipboard API, which is still experimental but should be used in the future instead of this snippet. Find out more about it here.
Copy a string to the clipboard. Only works as a result of user action (i.e. inside a click event listener).
Create a new <textarea> element, fill it with the supplied data and add it to the HTML document. Use Selection.getRangeAt()to store the selected range (if any). Use document.execCommand('copy') to copy to the clipboard. Remove the <textarea> element from the HTML document. Finally, use Selection().addRange() to recover the original selected range (if any).
const copyToClipboard = str => {
   const el = document.createElement('textarea');
   el.value = str;
   el.setAttribute('readonly', '');
@@ -101,7 +101,7 @@
   }
 };
 
copyToClipboard('Lorem ipsum'); // 'Lorem ipsum' copied to clipboard.
-
advanced
counter
Creates a counter with the specified range, step and duration for the specified selector.
Check if step has the proper sign and change it accordingly. Use setInterval() in combination with Math.abs() and Math.floor() to calculate the time between each new text draw. Use document.querySelector().innerHTML to update the value of the selected element. Omit the fourth parameter, step, to use a default step of 1. Omit the fifth parameter, duration, to use a default duration of 2000ms.
const counter = (selector, start, end, step = 1, duration = 2000) => {
+
counter
Creates a counter with the specified range, step and duration for the specified selector.
Check if step has the proper sign and change it accordingly. Use setInterval() in combination with Math.abs() and Math.floor() to calculate the time between each new text draw. Use document.querySelector().innerHTML to update the value of the selected element. Omit the fourth parameter, step, to use a default step of 1. Omit the fifth parameter, duration, to use a default duration of 2000ms.
const counter = (selector, start, end, step = 1, duration = 2000) => {
   let current = start,
     _step = (end - start) * step < 0 ? -step : step,
     timer = setInterval(() => {
@@ -113,7 +113,7 @@
   return timer;
 };
 
counter('#my-id', 1, 1000, 5, 2000); // Creates a 2-second timer for the element with id="my-id"
-
beginner
createElement
Creates an element from a string (without appending it to the document). If the given string contains multiple elements, only the first one will be returned.
Use document.createElement() to create a new element. Set its innerHTML to the string supplied as the argument. Use ParentNode.firstElementChild to return the element version of the string.
const createElement = str => {
+
createElement
Creates an element from a string (without appending it to the document). If the given string contains multiple elements, only the first one will be returned.
Use document.createElement() to create a new element. Set its innerHTML to the string supplied as the argument. Use ParentNode.firstElementChild to return the element version of the string.
const createElement = str => {
   const el = document.createElement('div');
   el.innerHTML = str;
   return el.firstElementChild;
@@ -124,7 +124,7 @@
   </div>`
 );
 console.log(el.className); // 'container'
-
advanced
createEventHub
Creates a pub/sub (publish–subscribe) event hub with emit, on, and off methods.
Use Object.create(null) to create an empty hub object that does not inherit properties from Object.prototype. For emit, resolve the array of handlers based on the event argument and then run each one with Array.forEach() by passing in the data as an argument. For on, create an array for the event if it does not yet exist, then use Array.push() to add the handler to the array. For off, use Array.findIndex() to find the index of the handler in the event array and remove it using Array.splice().
const createEventHub = () => ({
+
createEventHub
Creates a pub/sub (publish–subscribe) event hub with emit, on, and off methods.
Use Object.create(null) to create an empty hub object that does not inherit properties from Object.prototype. For emit, resolve the array of handlers based on the event argument and then run each one with Array.forEach() by passing in the data as an argument. For on, create an array for the event if it does not yet exist, then use Array.push() to add the handler to the array. For off, use Array.findIndex() to find the index of the handler in the event array and remove it using Array.splice().
const createEventHub = () => ({
   hub: Object.create(null),
   emit(event, data) {
     (this.hub[event] || []).forEach(handler => handler(data));
@@ -154,17 +154,17 @@ hub.emit// Unsubscribe: stop a specific handler from listening to the 'message' event
 hub.off('message', handler);
-
beginner
currentURL
Returns the current URL.
Use window.location.href to get current URL.
const currentURL = () => window.location.href;
+
currentURL
Returns the current URL.
Use window.location.href to get current URL.
const currentURL = () => window.location.href;
 
currentURL(); // 'https://google.com'
-
intermediate
detectDeviceType
Detects wether the website is being opened in a mobile device or a desktop/laptop.
Use a regular expression to test the navigator.userAgent property to figure out if the device is a mobile device or a desktop/laptop.
const detectDeviceType = () =>
+
detectDeviceType
Detects wether the website is being opened in a mobile device or a desktop/laptop.
Use a regular expression to test the navigator.userAgent property to figure out if the device is a mobile device or a desktop/laptop.
const detectDeviceType = () =>
   /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)
     ? 'Mobile'
     : 'Desktop';
 
detectDeviceType(); // "Mobile" or "Desktop"
-
intermediate
elementContains
Returns true if the parent element contains the child element, false otherwise.
Check that parent is not the same element as child, use parent.contains(child) to check if the parent element contains the child element.
const elementContains = (parent, child) => parent !== child && parent.contains(child);
+
elementContains
Returns true if the parent element contains the child element, false otherwise.
Check that parent is not the same element as child, use parent.contains(child) to check if the parent element contains the child element.
const elementContains = (parent, child) => parent !== child && parent.contains(child);
 
elementContains(document.querySelector('head'), document.querySelector('title')); // true
 elementContains(document.querySelector('body'), document.querySelector('body')); // false
-
advanced
elementIsVisibleInViewport
Returns true if the element specified is visible in the viewport, false otherwise.
Use Element.getBoundingClientRect() and the window.inner(Width|Height) values to determine if a given element is visible in the viewport. Omit the second argument to determine if the element is entirely visible, or specify true to determine if it is partially visible.
const elementIsVisibleInViewport = (el, partiallyVisible = false) => {
+
elementIsVisibleInViewport
Returns true if the element specified is visible in the viewport, false otherwise.
Use Element.getBoundingClientRect() and the window.inner(Width|Height) values to determine if a given element is visible in the viewport. Omit the second argument to determine if the element is entirely visible, or specify true to determine if it is partially visible.
const elementIsVisibleInViewport = (el, partiallyVisible = false) => {
   const { top, left, bottom, right } = el.getBoundingClientRect();
   const { innerHeight, innerWidth } = window;
   return partiallyVisible
@@ -175,16 +175,16 @@ hub.off
// e.g. 100x100 viewport and a 10x10px element at position {top: -1, left: 0, bottom: 9, right: 10}
 elementIsVisibleInViewport(el); // false - (not fully visible)
 elementIsVisibleInViewport(el, true); // true - (partially visible)
-
intermediate
getScrollPosition
Returns the scroll position of the current page.
Use pageXOffset and pageYOffset if they are defined, otherwise scrollLeft and scrollTop. You can omit el to use a default value of window.
const getScrollPosition = (el = window) => ({
+
getScrollPosition
Returns the scroll position of the current page.
Use pageXOffset and pageYOffset if they are defined, otherwise scrollLeft and scrollTop. You can omit el to use a default value of window.
const getScrollPosition = (el = window) => ({
   x: el.pageXOffset !== undefined ? el.pageXOffset : el.scrollLeft,
   y: el.pageYOffset !== undefined ? el.pageYOffset : el.scrollTop
 });
 
getScrollPosition(); // {x: 0, y: 200}
-
beginner
getStyle
Returns the value of a CSS rule for the specified element.
Use Window.getComputedStyle() to get the value of the CSS rule for the specified element.
const getStyle = (el, ruleName) => getComputedStyle(el)[ruleName];
+
getStyle
Returns the value of a CSS rule for the specified element.
Use Window.getComputedStyle() to get the value of the CSS rule for the specified element.
const getStyle = (el, ruleName) => getComputedStyle(el)[ruleName];
 
getStyle(document.querySelector('p'), 'font-size'); // '16px'
-
beginner
hasClass
Returns true if the element has the specified class, false otherwise.
Use element.classList.contains() to check if the element has the specified class.
const hasClass = (el, className) => el.classList.contains(className);
+
hasClass
Returns true if the element has the specified class, false otherwise.
Use element.classList.contains() to check if the element has the specified class.
const hasClass = (el, className) => el.classList.contains(className);
 
hasClass(document.querySelector('p.special'), 'special'); // true
-
advanced
hashBrowser
Creates a hash for a value using the SHA-256 algorithm. Returns a promise.
Use the SubtleCrypto API to create a hash for the given value.
const hashBrowser = val =>
+
hashBrowser
Creates a hash for a value using the SHA-256 algorithm. Returns a promise.
Use the SubtleCrypto API to create a hash for the given value.
const hashBrowser = val =>
   crypto.subtle.digest('SHA-256', new TextEncoder('utf-8').encode(val)).then(h => {
     let hexes = [],
       view = new DataView(h);
@@ -193,21 +193,21 @@ hub.offreturn hexes.join('');
   });
 
hashBrowser(JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })).then(console.log); // '04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393'
-
beginner
hide
Hides all the elements specified.
Use NodeList.prototype.forEach() to apply display: none to each element specified.
const hide = els => els.forEach(e => (e.style.display = 'none'));
+
hide
Hides all the elements specified.
Use NodeList.prototype.forEach() to apply display: none to each element specified.
const hide = els => els.forEach(e => (e.style.display = 'none'));
 
hide(document.querySelectorAll('img')); // Hides all <img> elements on the page
-
intermediate
httpsRedirect
Redirects the page to HTTPS if its currently in HTTP. Also, pressing the back button doesn't take it back to the HTTP page as its replaced in the history.
Use location.protocol to get the protocol currently being used. If it's not HTTPS, use location.replace() to replace the existing page with the HTTPS version of the page. Use location.href to get the full address, split it with String.split() and remove the protocol part of the URL.
const httpsRedirect = () => {
+
httpsRedirect
Redirects the page to HTTPS if its currently in HTTP. Also, pressing the back button doesn't take it back to the HTTP page as its replaced in the history.
Use location.protocol to get the protocol currently being used. If it's not HTTPS, use location.replace() to replace the existing page with the HTTPS version of the page. Use location.href to get the full address, split it with String.split() and remove the protocol part of the URL.
const httpsRedirect = () => {
   if (location.protocol !== 'https:') location.replace('https://' + location.href.split('//')[1]);
 };
 
httpsRedirect(); // If you are on http://mydomain.com, you are redirected to https://mydomain.com
-
beginner
insertAfter
Inserts an HTML string after the end of the specified element.
Use el.insertAdjacentHTML() with a position of 'afterend' to parse htmlString and insert it after the end of el.
const insertAfter = (el, htmlString) => el.insertAdjacentHTML('afterend', htmlString);
+
insertAfter
Inserts an HTML string after the end of the specified element.
Use el.insertAdjacentHTML() with a position of 'afterend' to parse htmlString and insert it after the end of el.
const insertAfter = (el, htmlString) => el.insertAdjacentHTML('afterend', htmlString);
 
insertAfter(document.getElementById('myId'), '<p>after</p>'); // <div id="myId">...</div> <p>after</p>
-
beginner
insertBefore
Inserts an HTML string before the start of the specified element.
Use el.insertAdjacentHTML() with a position of 'beforebegin' to parse htmlString and insert it before the start of el.
const insertBefore = (el, htmlString) => el.insertAdjacentHTML('beforebegin', htmlString);
+
insertBefore
Inserts an HTML string before the start of the specified element.
Use el.insertAdjacentHTML() with a position of 'beforebegin' to parse htmlString and insert it before the start of el.
const insertBefore = (el, htmlString) => el.insertAdjacentHTML('beforebegin', htmlString);
 
insertBefore(document.getElementById('myId'), '<p>before</p>'); // <p>before</p> <div id="myId">...</div>
-
beginner
isBrowserTabFocused
Returns true if the browser tab of the page is focused, false otherwise.
Use the Document.hidden property, introduced by the Page Visibility API to check if the browser tab of the page is visible or hidden.
const isBrowserTabFocused = () => !document.hidden;
+
isBrowserTabFocused
Returns true if the browser tab of the page is focused, false otherwise.
Use the Document.hidden property, introduced by the Page Visibility API to check if the browser tab of the page is visible or hidden.
const isBrowserTabFocused = () => !document.hidden;
 
isBrowserTabFocused(); // true
-
beginner
nodeListToArray
Converts a NodeList to an array.
Use spread operator inside new array to convert a NodeList to an array.
const nodeListToArray = nodeList => [...nodeList];
+
nodeListToArray
Converts a NodeList to an array.
Use spread operator inside new array to convert a NodeList to an array.
const nodeListToArray = nodeList => [...nodeList];
 
nodeListToArray(document.childNodes); // [ <!DOCTYPE html>, html ]
-
advanced
observeMutations
Returns a new MutationObserver and runs the provided callback for each mutation on the specified element.
Use a MutationObserver to observe mutations on the given element. Use Array.forEach() to run the callback for each mutation that is observed. Omit the third argument, options, to use the default options (all true).
const observeMutations = (element, callback, options) => {
+
observeMutations
Returns a new MutationObserver and runs the provided callback for each mutation on the specified element.
Use a MutationObserver to observe mutations on the given element. Use Array.forEach() to run the callback for each mutation that is observed. Omit the third argument, options, to use the default options (all true).
const observeMutations = (element, callback, options) => {
   const observer = new MutationObserver(mutations => mutations.forEach(m => callback(m)));
   observer.observe(
     element,
@@ -227,11 +227,11 @@ hub.off
 
const obs = observeMutations(document, console.log); // Logs all mutations that happen on the page
 obs.disconnect(); // Disconnects the observer and stops logging mutations on the page
-
intermediate
off
Removes an event listener from an element.
Use EventTarget.removeEventListener() to remove an event listener from an element. Omit the fourth argument opts to use false or specify it based on the options used when the event listener was added.
const off = (el, evt, fn, opts = false) => el.removeEventListener(evt, fn, opts);
+
off
Removes an event listener from an element.
Use EventTarget.removeEventListener() to remove an event listener from an element. Omit the fourth argument opts to use false or specify it based on the options used when the event listener was added.
const off = (el, evt, fn, opts = false) => el.removeEventListener(evt, fn, opts);
 
const fn = () => console.log('!');
 document.body.addEventListener('click', fn);
 off(document.body, 'click', fn); // no longer logs '!' upon clicking on the page
-
intermediate
on
Adds an event listener to an element with the ability to use event delegation.
Use EventTarget.addEventListener() to add an event listener to an element. If there is a target property supplied to the options object, ensure the event target matches the target specified and then invoke the callback by supplying the correct this context. Returns a reference to the custom delegator function, in order to be possible to use with off. Omit opts to default to non-delegation behavior and event bubbling.
const on = (el, evt, fn, opts = {}) => {
+
on
Adds an event listener to an element with the ability to use event delegation.
Use EventTarget.addEventListener() to add an event listener to an element. If there is a target property supplied to the options object, ensure the event target matches the target specified and then invoke the callback by supplying the correct this context. Returns a reference to the custom delegator function, in order to be possible to use with off. Omit opts to default to non-delegation behavior and event bubbling.
const on = (el, evt, fn, opts = {}) => {
   const delegatorFn = e => e.target.matches(opts.target) && fn.call(e.target, e);
   el.addEventListener(evt, opts.target ? delegatorFn : fn, opts.options || false);
   if (opts.target) return delegatorFn;
@@ -240,7 +240,7 @@ document.bodyon(document.body, 'click', fn); // logs '!' upon clicking the body
 on(document.body, 'click', fn, { target: 'p' }); // logs '!' upon clicking a `p` element child of the body
 on(document.body, 'click', fn, { options: true }); // use capturing instead of bubbling
-
advanced
onUserInputChange
Run the callback whenever the user input type changes (mouse or touch). Useful for enabling/disabling code depending on the input device. This process is dynamic and works with hybrid devices (e.g. touchscreen laptops).
Use two event listeners. Assume mouse input initially and bind a touchstart event listener to the document. On touchstart, add a mousemove event listener to listen for two consecutive mousemove events firing within 20ms, using performance.now(). Run the callback with the input type as an argument in either of these situations.
const onUserInputChange = callback => {
+
onUserInputChange
Run the callback whenever the user input type changes (mouse or touch). Useful for enabling/disabling code depending on the input device. This process is dynamic and works with hybrid devices (e.g. touchscreen laptops).
Use two event listeners. Assume mouse input initially and bind a touchstart event listener to the document. On touchstart, add a mousemove event listener to listen for two consecutive mousemove events firing within 20ms, using performance.now(). Run the callback with the input type as an argument in either of these situations.
const onUserInputChange = callback => {
   let type = 'mouse',
     lastTime = 0;
   const mousemoveHandler = () => {
@@ -257,7 +257,7 @@ document.bodyexamples
onUserInputChange(type => {
   console.log('The user is now using', type, 'as an input method.');
 });
-
intermediate
prefix
Returns the prefixed version (if necessary) of a CSS property that the browser supports.
Use Array.findIndex() on an array of vendor prefix strings to test if document.body has one of them defined in its CSSStyleDeclaration object, otherwise return null. Use String.charAt() and String.toUpperCase() to capitalize the property, which will be appended to the vendor prefix string.
const prefix = prop => {
+
prefix
Returns the prefixed version (if necessary) of a CSS property that the browser supports.
Use Array.findIndex() on an array of vendor prefix strings to test if document.body has one of them defined in its CSSStyleDeclaration object, otherwise return null. Use String.charAt() and String.toUpperCase() to capitalize the property, which will be appended to the vendor prefix string.
const prefix = prop => {
   const capitalizedProp = prop.charAt(0).toUpperCase() + prop.slice(1);
   const prefixes = ['', 'webkit', 'moz', 'ms', 'o'];
   const i = prefixes.findIndex(
@@ -266,7 +266,7 @@ document.bodyreturn i !== -1 ? (i === 0 ? prop : prefixes[i] + capitalizedProp) : null;
 };
 
prefix('appearance'); // 'appearance' on a supported browser, otherwise 'webkitAppearance', 'mozAppearance', 'msAppearance' or 'oAppearance'
-
intermediate
recordAnimationFrames
Invokes the provided callback on each animation frame.
Use recursion. Provided that running is true, continue invoking window.requestAnimationFrame() which invokes the provided callback. Return an object with two methods start and stop to allow manual control of the recording. Omit the second argument, autoStart, to implicitly call start when the function is invoked.
const recordAnimationFrames = (callback, autoStart = true) => {
+
recordAnimationFrames
Invokes the provided callback on each animation frame.
Use recursion. Provided that running is true, continue invoking window.requestAnimationFrame() which invokes the provided callback. Return an object with two methods start and stop to allow manual control of the recording. Omit the second argument, autoStart, to implicitly call start when the function is invoked.
const recordAnimationFrames = (callback, autoStart = true) => {
   let running = true,
     raf;
   const stop = () => {
@@ -291,10 +291,10 @@ document.body.stop(); // stops logging
 recorder.start(); // starts again
 const recorder2 = recordAnimationFrames(cb, false); // `start` needs to be explicitly called to begin recording frames
-
beginner
redirect
Redirects to a specified URL.
Use window.location.href or window.location.replace() to redirect to url. Pass a second argument to simulate a link click (true - default) or an HTTP redirect (false).
const redirect = (url, asLink = true) =>
+
redirect
Redirects to a specified URL.
Use window.location.href or window.location.replace() to redirect to url. Pass a second argument to simulate a link click (true - default) or an HTTP redirect (false).
const redirect = (url, asLink = true) =>
   asLink ? (window.location.href = url) : window.location.replace(url);
 
redirect('https://google.com');
-
advanced
runAsync
Runs a function in a separate thread by using a Web Worker, allowing long running functions to not block the UI.
Create a new Worker using a Blob object URL, the contents of which should be the stringified version of the supplied function. Immediately post the return value of calling the function back. Return a promise, listening for onmessage and onerror events and resolving the data posted back from the worker, or throwing an error.
const runAsync = fn => {
+
runAsync
Runs a function in a separate thread by using a Web Worker, allowing long running functions to not block the UI.
Create a new Worker using a Blob object URL, the contents of which should be the stringified version of the supplied function. Immediately post the return value of calling the function back. Return a promise, listening for onmessage and onerror events and resolving the data posted back from the worker, or throwing an error.
const runAsync = fn => {
   const worker = new Worker(
     URL.createObjectURL(new Blob([`postMessage((${fn})());`]), {
       type: 'application/javascript; charset=utf-8'
@@ -329,7 +329,7 @@ recorder.sta
 runAsync(() => 10 ** 3).then(console.log); // 1000
 let outsideVariable = 50;
 runAsync(() => typeof outsideVariable).then(console.log); // 'undefined'
-
intermediate
scrollToTop
Smooth-scrolls to the top of the page.
Get distance from top using document.documentElement.scrollTop or document.body.scrollTop. Scroll by a fraction of the distance from the top. Use window.requestAnimationFrame() to animate the scrolling.
const scrollToTop = () => {
+
scrollToTop
Smooth-scrolls to the top of the page.
Get distance from top using document.documentElement.scrollTop or document.body.scrollTop. Scroll by a fraction of the distance from the top. Use window.requestAnimationFrame() to animate the scrolling.
const scrollToTop = () => {
   const c = document.documentElement.scrollTop || document.body.scrollTop;
   if (c > 0) {
     window.requestAnimationFrame(scrollToTop);
@@ -337,25 +337,25 @@ recorder.sta
   }
 };
 
scrollToTop();
-
beginner
setStyle
Sets the value of a CSS rule for the specified element.
Use element.style to set the value of the CSS rule for the specified element to val.
const setStyle = (el, ruleName, val) => (el.style[ruleName] = val);
+
setStyle
Sets the value of a CSS rule for the specified element.
Use element.style to set the value of the CSS rule for the specified element to val.
const setStyle = (el, ruleName, val) => (el.style[ruleName] = val);
 
setStyle(document.querySelector('p'), 'font-size', '20px'); // The first <p> element on the page will have a font-size of 20px
-
beginner
show
Shows all the elements specified.
Use the spread operator (...) and Array.forEach() to clear the display property for each element specified.
const show = (...el) => [...el].forEach(e => (e.style.display = ''));
+
show
Shows all the elements specified.
Use the spread operator (...) and Array.forEach() to clear the display property for each element specified.
const show = (...el) => [...el].forEach(e => (e.style.display = ''));
 
show(...document.querySelectorAll('img')); // Shows all <img> elements on the page
-
intermediate
smoothScroll
Smoothly scrolls the element on which it's called into the visible area of the browser window.
Use .scrollIntoView method to scroll the element. Pass { behavior: 'smooth' } to .scrollIntoView so it scrolls smoothly.
const smoothScroll = element =>
+
smoothScroll
Smoothly scrolls the element on which it's called into the visible area of the browser window.
Use .scrollIntoView method to scroll the element. Pass { behavior: 'smooth' } to .scrollIntoView so it scrolls smoothly.
const smoothScroll = element =>
   document.querySelector(element).scrollIntoView({
     behavior: 'smooth'
   });
 
smoothScroll('#fooBar'); // scrolls smoothly to the element with the id fooBar
 smoothScroll('.fooBar'); // scrolls smoothly to the first element with a class of fooBar
-
beginner
toggleClass
Toggle a class for an element.
Use element.classList.toggle() to toggle the specified class for the element.
const toggleClass = (el, className) => el.classList.toggle(className);
+
toggleClass
Toggle a class for an element.
Use element.classList.toggle() to toggle the specified class for the element.
const toggleClass = (el, className) => el.classList.toggle(className);
 
toggleClass(document.querySelector('p.special'), 'special'); // The paragraph will not have the 'special' class anymore
-
intermediate
triggerEvent
Triggers a specific event on a given element, optionally passing custom data.
Use new CustomEvent() to create an event from the specified eventType and details. Use el.dispatchEvent() to trigger the newly created event on the given element. Omit the third argument, detail, if you do not want to pass custom data to the triggered event.
const triggerEvent = (el, eventType, detail = undefined) =>
+
triggerEvent
Triggers a specific event on a given element, optionally passing custom data.
Use new CustomEvent() to create an event from the specified eventType and details. Use el.dispatchEvent() to trigger the newly created event on the given element. Omit the third argument, detail, if you do not want to pass custom data to the triggered event.
const triggerEvent = (el, eventType, detail = undefined) =>
   el.dispatchEvent(new CustomEvent(eventType, { detail: detail }));
 
triggerEvent(document.getElementById('myId'), 'click');
 triggerEvent(document.getElementById('myId'), 'click', { username: 'bob' });
-
intermediate
UUIDGeneratorBrowser
Generates a UUID in a browser.
Use crypto API to generate a UUID, compliant with RFC4122 version 4.
const UUIDGeneratorBrowser = () =>
+
UUIDGeneratorBrowser
Generates a UUID in a browser.
Use crypto API to generate a UUID, compliant with RFC4122 version 4.
const UUIDGeneratorBrowser = () =>
   ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
     (c ^ (crypto.getRandomValues(new Uint8Array(1))[0] & (15 >> (c / 4)))).toString(16)
   );
 
UUIDGeneratorBrowser(); // '7982fcfe-5721-4632-bede-6000885be57d'
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/contributing.html b/docs/contributing.html index a3b47913b..ba8c610e6 100644 --- a/docs/contributing.html +++ b/docs/contributing.html @@ -66,7 +66,7 @@ license.
Logos made by Angelos Chalaris and ribbon made by Tim Holman are licensed under the MIT license.
Sponsored by DigitalOcean.

+ width="20px" height="20px" alt="DigitalOcean">DigitalOcean.


About    Contributing    Archive    Glossary

diff --git a/docs/date.html b/docs/date.html index 4bf3f826e..e1e8fde02 100644 --- a/docs/date.html +++ b/docs/date.html @@ -73,7 +73,7 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Date

intermediate

formatDuration

Returns the human readable format of the given number of milliseconds.

Divide ms with the appropriate values to obtain the appropriate values for day, hour, minute, second and millisecond. Use Object.entries() with Array.filter() to keep only non-zero values. Use Array.map() to create the string for each value, pluralizing appropriately. Use String.join(', ') to combine the values into a string.

const formatDuration = ms => {
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Date
formatDuration
Returns the human readable format of the given number of milliseconds.
Divide ms with the appropriate values to obtain the appropriate values for day, hour, minute, second and millisecond. Use Object.entries() with Array.filter() to keep only non-zero values. Use Array.map() to create the string for each value, pluralizing appropriately. Use String.join(', ') to combine the values into a string.
const formatDuration = ms => {
   if (ms < 0) ms = -ms;
   const time = {
     day: Math.floor(ms / 86400000),
@@ -89,12 +89,12 @@
 };
 
formatDuration(1001); // '1 second, 1 millisecond'
 formatDuration(34325055574); // '397 days, 6 hours, 44 minutes, 15 seconds, 574 milliseconds'
-
intermediate
getColonTimeFromDate
Returns a string of the form HH:MM:SS from a Date object.
Use Date.toString() and String.slice() to get the HH:MM:SS part of a given Date object.
const getColonTimeFromDate = date => date.toTimeString().slice(0, 8);
+
getColonTimeFromDate
Returns a string of the form HH:MM:SS from a Date object.
Use Date.toString() and String.slice() to get the HH:MM:SS part of a given Date object.
const getColonTimeFromDate = date => date.toTimeString().slice(0, 8);
 
getColonTimeFromDate(new Date()); // "08:38:00"
-
intermediate
getDaysDiffBetweenDates
Returns the difference (in days) between two dates.
Calculate the difference (in days) between two Date objects.
const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>
+
getDaysDiffBetweenDates
Returns the difference (in days) between two dates.
Calculate the difference (in days) between two Date objects.
const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>
   (dateFinal - dateInitial) / (1000 * 3600 * 24);
 
getDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')); // 9
-
beginner
getMeridiemSuffixOfInteger
Converts an integer to a suffixed string, adding am or pm based on its value.
Use the modulo operator (%) and conditional checks to transform an integer to a stringified 12-hour format with meridiem suffix.
const getMeridiemSuffixOfInteger = num =>
+
getMeridiemSuffixOfInteger
Converts an integer to a suffixed string, adding am or pm based on its value.
Use the modulo operator (%) and conditional checks to transform an integer to a stringified 12-hour format with meridiem suffix.
const getMeridiemSuffixOfInteger = num =>
   num === 0 || num === 24
     ? 12 + 'am'
     : num === 12
@@ -106,7 +106,7 @@
 getMeridiemSuffixOfInteger(11); // "11am"
 getMeridiemSuffixOfInteger(13); // "1pm"
 getMeridiemSuffixOfInteger(25); // "1pm"
-
intermediate
tomorrow
Results in a string representation of tomorrow's date. Use new Date() to get today's date, adding one day using Date.getDate() and Date.setDate(), and converting the Date object to a string.
const tomorrow = (long = false) => {
+
tomorrow
Results in a string representation of tomorrow's date. Use new Date() to get today's date, adding one day using Date.getDate() and Date.setDate(), and converting the Date object to a string.
const tomorrow = (long = false) => {
   let t = new Date();
   t.setDate(t.getDate() + 1);
   const ret = `${t.getFullYear()}-${String(t.getMonth() + 1).padStart(2, '0')}-${String(
@@ -116,4 +116,4 @@
 };
 
tomorrow(); // 2017-12-27 (if current date is 2017-12-26)
 tomorrow(true); // 2017-12-27T00:00:00 (if current date is 2017-12-26)
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/function.html b/docs/function.html index c0896a347..9f789435f 100644 --- a/docs/function.html +++ b/docs/function.html @@ -73,7 +73,7 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Function

intermediate

attempt

Attempts to invoke a function with the provided arguments, returning either the result or the caught error object.

Use a try... catch block to return either the result of the function or an appropriate error.

const attempt = (fn, ...args) => {
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Function
attempt
Attempts to invoke a function with the provided arguments, returning either the result or the caught error object.
Use a try... catch block to return either the result of the function or an appropriate error.
const attempt = (fn, ...args) => {
   try {
     return fn(...args);
   } catch (e) {
@@ -84,14 +84,14 @@
   return document.querySelectorAll(selector);
 }, '>_>');
 if (elements instanceof Error) elements = []; // elements = []
-
intermediate
bind
Creates a function that invokes fn with a given context, optionally adding any additional supplied parameters to the beginning of the arguments.
Return a function that uses Function.apply() to apply the given context to fn. Use Array.concat() to prepend any additional supplied parameters to the arguments.
const bind = (fn, context, ...boundArgs) => (...args) => fn.apply(context, [...boundArgs, ...args]);
+
bind
Creates a function that invokes fn with a given context, optionally adding any additional supplied parameters to the beginning of the arguments.
Return a function that uses Function.apply() to apply the given context to fn. Use Array.concat() to prepend any additional supplied parameters to the arguments.
const bind = (fn, context, ...boundArgs) => (...args) => fn.apply(context, [...boundArgs, ...args]);
 
function greet(greeting, punctuation) {
   return greeting + ' ' + this.user + punctuation;
 }
 const freddy = { user: 'fred' };
 const freddyBound = bind(greet, freddy);
 console.log(freddyBound('hi', '!')); // 'hi fred!'
-
intermediate
bindKey
Creates a function that invokes the method at a given key of an object, optionally adding any additional supplied parameters to the beginning of the arguments.
Return a function that uses Function.apply() to bind context[fn] to context. Use the spread operator (...) to prepend any additional supplied parameters to the arguments.
const bindKey = (context, fn, ...boundArgs) => (...args) =>
+
bindKey
Creates a function that invokes the method at a given key of an object, optionally adding any additional supplied parameters to the beginning of the arguments.
Return a function that uses Function.apply() to bind context[fn] to context. Use the spread operator (...) to prepend any additional supplied parameters to the arguments.
const bindKey = (context, fn, ...boundArgs) => (...args) =>
   context[fn].apply(context, [...boundArgs, ...args]);
 
const freddy = {
   user: 'fred',
@@ -101,7 +101,7 @@ console.log<
 };
 const freddyBound = bindKey(freddy, 'greet');
 console.log(freddyBound('hi', '!')); // 'hi fred!'
-
intermediate
chainAsync
Chains asynchronous functions.
Loop through an array of functions containing asynchronous events, calling next when each asynchronous event has completed.
const chainAsync = fns => {
+
chainAsync
Chains asynchronous functions.
Loop through an array of functions containing asynchronous events, calling next when each asynchronous event has completed.
const chainAsync = fns => {
   let curr = 0;
   const next = () => fns[curr++](next);
   next();
@@ -115,7 +115,7 @@ console.log<
     console.log('1 second');
   }
 ]);
-
intermediate
compose
Performs right-to-left function composition.
Use Array.reduce() to perform right-to-left function composition. The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));
+
compose
Performs right-to-left function composition.
Use Array.reduce() to perform right-to-left function composition. The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));
 
const add5 = x => x + 5;
 const multiply = (x, y) => x * y;
 const multiplyAndAdd5 = compose(
@@ -123,22 +123,22 @@ console.log<
   multiply
 );
 multiplyAndAdd5(5, 2); // 15
-
intermediate
composeRight
Performs left-to-right function composition.
Use Array.reduce() to perform left-to-right function composition. The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
const composeRight = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)));
+
composeRight
Performs left-to-right function composition.
Use Array.reduce() to perform left-to-right function composition. The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
const composeRight = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)));
 
const add = (x, y) => x + y;
 const square = x => x * x;
 const addAndSquare = composeRight(add, square);
 addAndSquare(1, 2); // 9
-
intermediate
converge
Accepts a converging function and a list of branching functions and returns a function that applies each branching function to the arguments and the results of the branching functions are passed as arguments to the converging function.
Use Array.map() and Function.apply() to apply each function to the given arguments. Use the spread operator (...) to call coverger with the results of all other functions.
const converge = (converger, fns) => (...args) => converger(...fns.map(fn => fn.apply(null, args)));
+
converge
Accepts a converging function and a list of branching functions and returns a function that applies each branching function to the arguments and the results of the branching functions are passed as arguments to the converging function.
Use Array.map() and Function.apply() to apply each function to the given arguments. Use the spread operator (...) to call coverger with the results of all other functions.
const converge = (converger, fns) => (...args) => converger(...fns.map(fn => fn.apply(null, args)));
 
const average = converge((a, b) => a / b, [
   arr => arr.reduce((a, v) => a + v, 0),
   arr => arr.length
 ]);
 average([1, 2, 3, 4, 5, 6, 7]); // 4
-
intermediate
curry
Curries a function.
Use recursion. If the number of provided arguments (args) is sufficient, call the passed function fn. Otherwise, return a curried function fn that expects the rest of the arguments. If you want to curry a function that accepts a variable number of arguments (a variadic function, e.g. Math.min()), you can optionally pass the number of arguments to the second parameter arity.
const curry = (fn, arity = fn.length, ...args) =>
+
curry
Curries a function.
Use recursion. If the number of provided arguments (args) is sufficient, call the passed function fn. Otherwise, return a curried function fn that expects the rest of the arguments. If you want to curry a function that accepts a variable number of arguments (a variadic function, e.g. Math.min()), you can optionally pass the number of arguments to the second parameter arity.
const curry = (fn, arity = fn.length, ...args) =>
   arity <= args.length ? fn(...args) : curry.bind(null, fn, arity, ...args);
 
curry(Math.pow)(2)(10); // 1024
 curry(Math.min, 3)(10)(50)(2); // 2
-
intermediate
debounce
Creates a debounced function that delays invoking the provided function until at least ms milliseconds have elapsed since the last time it was invoked.
Each time the debounced function is invoked, clear the current pending timeout with clearTimeout() and use setTimeout() to create a new timeout that delays invoking the function until at least ms milliseconds has elapsed. Use Function.apply() to apply the this context to the function and provide the necessary arguments. Omit the second argument, ms, to set the timeout at a default of 0 ms.
const debounce = (fn, ms = 0) => {
+
debounce
Creates a debounced function that delays invoking the provided function until at least ms milliseconds have elapsed since the last time it was invoked.
Each time the debounced function is invoked, clear the current pending timeout with clearTimeout() and use setTimeout() to create a new timeout that delays invoking the function until at least ms milliseconds has elapsed. Use Function.apply() to apply the this context to the function and provide the necessary arguments. Omit the second argument, ms, to set the timeout at a default of 0 ms.
const debounce = (fn, ms = 0) => {
   let timeoutId;
   return function(...args) {
     clearTimeout(timeoutId);
@@ -152,7 +152,7 @@ console.log<
     console.log(window.innerHeight);
   }, 250)
 ); // Will log the window dimensions at most every 250ms
-
intermediate
defer
Defers invoking a function until the current call stack has cleared.
Use setTimeout() with a timeout of 1ms to add a new event to the browser event queue and allow the rendering engine to complete its work. Use the spread (...) operator to supply the function with an arbitrary number of arguments.
const defer = (fn, ...args) => setTimeout(fn, 1, ...args);
+
defer
Defers invoking a function until the current call stack has cleared.
Use setTimeout() with a timeout of 1ms to add a new event to the browser event queue and allow the rendering engine to complete its work. Use the spread (...) operator to supply the function with an arbitrary number of arguments.
const defer = (fn, ...args) => setTimeout(fn, 1, ...args);
 
// Example A:
 defer(console.log, 'a'), console.log('b'); // logs 'b' then 'a'
 
@@ -160,7 +160,7 @@ console.log<
 document.querySelector('#someElement').innerHTML = 'Hello';
 longRunningFunction(); //Browser will not update the HTML until this has finished
 defer(longRunningFunction); // Browser will update the HTML then run the function
-
intermediate
delay
Invokes the provided function after wait milliseconds.
Use setTimeout() to delay execution of fn. Use the spread (...) operator to supply the function with an arbitrary number of arguments.
const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args);
+
delay
Invokes the provided function after wait milliseconds.
Use setTimeout() to delay execution of fn. Use the spread (...) operator to supply the function with an arbitrary number of arguments.
const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args);
 
delay(
   function(text) {
     console.log(text);
@@ -168,9 +168,9 @@ document.que
   1000,
   'later'
 ); // Logs 'later' after one second.
-
beginner
functionName
Logs the name of a function.
Use console.debug() and the name property of the passed method to log the method's name to the debug channel of the console.
const functionName = fn => (console.debug(fn.name), fn);
+
functionName
Logs the name of a function.
Use console.debug() and the name property of the passed method to log the method's name to the debug channel of the console.
const functionName = fn => (console.debug(fn.name), fn);
 
functionName(Math.max); // max (logged in debug channel of console)
-
intermediate
hz
Returns the number of times a function executed per second. hz is the unit for hertz, the unit of frequency defined as one cycle per second.
Use performance.now() to get the difference in milliseconds before and after the iteration loop to calculate the time elapsed executing the function iterations times. Return the number of cycles per second by converting milliseconds to seconds and dividing it by the time elapsed. Omit the second argument, iterations, to use the default of 100 iterations.
const hz = (fn, iterations = 100) => {
+
hz
Returns the number of times a function executed per second. hz is the unit for hertz, the unit of frequency defined as one cycle per second.
Use performance.now() to get the difference in milliseconds before and after the iteration loop to calculate the time elapsed executing the function iterations times. Return the number of cycles per second by converting milliseconds to seconds and dividing it by the time elapsed. Omit the second argument, iterations, to use the default of 100 iterations.
const hz = (fn, iterations = 100) => {
   const before = performance.now();
   for (let i = 0; i < iterations; i++) fn();
   return (1000 * iterations) / (performance.now() - before);
@@ -191,7 +191,7 @@ document.que
 // `sumForLoop` is nearly 10 times faster
 Math.round(hz(sumReduce)); // 572
 Math.round(hz(sumForLoop)); // 4784
-
advanced
memoize
Returns the memoized (cached) function.
Create an empty cache by instantiating a new Map object. Return a function which takes a single argument to be supplied to the memoized function by first checking if the function's output for that specific input value is already cached, or store and return it if not. The function keyword must be used in order to allow the memoized function to have its this context changed if necessary. Allow access to the cache by setting it as a property on the returned function.
const memoize = fn => {
+
memoize
Returns the memoized (cached) function.
Create an empty cache by instantiating a new Map object. Return a function which takes a single argument to be supplied to the memoized function by first checking if the function's output for that specific input value is already cached, or store and return it if not. The function keyword must be used in order to allow the memoized function to have its this context changed if necessary. Allow access to the cache by setting it as a property on the returned function.
const memoize = fn => {
   const cache = new Map();
   const cached = function(val) {
     return cache.has(val) ? cache.get(val) : cache.set(val, fn.call(this, val)) && cache.get(val);
@@ -204,9 +204,9 @@ Math.roundanagramsCached('javascript'); // takes a long time
 anagramsCached('javascript'); // returns virtually instantly since it's now cached
 console.log(anagramsCached.cache); // The cached anagrams map
-
beginner
negate
Negates a predicate function.
Take a predicate function and apply the not operator (!) to it with its arguments.
const negate = func => (...args) => !func(...args);
+
negate
Negates a predicate function.
Take a predicate function and apply the not operator (!) to it with its arguments.
const negate = func => (...args) => !func(...args);
 
[1, 2, 3, 4, 5, 6].filter(negate(n => n % 2 === 0)); // [ 1, 3, 5 ]
-
intermediate
once
Ensures a function is called only once.
Utilizing a closure, use a flag, called, and set it to true once the function is called for the first time, preventing it from being called again. In order to allow the function to have its this context changed (such as in an event listener), the function keyword must be used, and the supplied function must have the context applied. Allow the function to be supplied with an arbitrary number of arguments using the rest/spread (...) operator.
const once = fn => {
+
once
Ensures a function is called only once.
Utilizing a closure, use a flag, called, and set it to true once the function is called for the first time, preventing it from being called again. In order to allow the function to have its this context changed (such as in an event listener), the function keyword must be used, and the supplied function must have the context applied. Allow the function to be supplied with an arbitrary number of arguments using the rest/spread (...) operator.
const once = fn => {
   let called = false;
   return function(...args) {
     if (called) return;
@@ -218,24 +218,24 @@ console.log<
   console.log(this, event); // document.body, MouseEvent
 };
 document.body.addEventListener('click', once(startApp)); // only runs `startApp` once upon click
-
intermediate
partial
Creates a function that invokes fn with partials prepended to the arguments it receives.
Use the spread operator (...) to prepend partials to the list of arguments of fn.
const partial = (fn, ...partials) => (...args) => fn(...partials, ...args);
+
partial
Creates a function that invokes fn with partials prepended to the arguments it receives.
Use the spread operator (...) to prepend partials to the list of arguments of fn.
const partial = (fn, ...partials) => (...args) => fn(...partials, ...args);
 
const greet = (greeting, name) => greeting + ' ' + name + '!';
 const greetHello = partial(greet, 'Hello');
 greetHello('John'); // 'Hello John!'
-
intermediate
partialRight
Creates a function that invokes fn with partials appended to the arguments it receives.
Use the spread operator (...) to append partials to the list of arguments of fn.
const partialRight = (fn, ...partials) => (...args) => fn(...args, ...partials);
+
partialRight
Creates a function that invokes fn with partials appended to the arguments it receives.
Use the spread operator (...) to append partials to the list of arguments of fn.
const partialRight = (fn, ...partials) => (...args) => fn(...args, ...partials);
 
const greet = (greeting, name) => greeting + ' ' + name + '!';
 const greetJohn = partialRight(greet, 'John');
 greetJohn('Hello'); // 'Hello John!'
-
intermediate
runPromisesInSeries
Runs an array of promises in series.
Use Array.reduce() to create a promise chain, where each promise returns the next promise when resolved.
const runPromisesInSeries = ps => ps.reduce((p, next) => p.then(next), Promise.resolve());
+
runPromisesInSeries
Runs an array of promises in series.
Use Array.reduce() to create a promise chain, where each promise returns the next promise when resolved.
const runPromisesInSeries = ps => ps.reduce((p, next) => p.then(next), Promise.resolve());
 
const delay = d => new Promise(r => setTimeout(r, d));
 runPromisesInSeries([() => delay(1000), () => delay(2000)]); // Executes each promise sequentially, taking a total of 3 seconds to complete
-
intermediate
sleep
Delays the execution of an asynchronous function.
Delay executing part of an async function, by putting it to sleep, returning a Promise.
const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));
+
sleep
Delays the execution of an asynchronous function.
Delay executing part of an async function, by putting it to sleep, returning a Promise.
const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));
 
async function sleepyWork() {
   console.log("I'm going to sleep for 1 second.");
   await sleep(1000);
   console.log('I woke up after 1 second.');
 }
-
advanced
throttle
Creates a throttled function that only invokes the provided function at most once per every wait milliseconds
Use setTimeout() and clearTimeout() to throttle the given method, fn. Use Function.apply() to apply the this context to the function and provide the necessary arguments. Use Date.now() to keep track of the last time the throttled function was invoked. Omit the second argument, wait, to set the timeout at a default of 0 ms.
const throttle = (fn, wait) => {
+
throttle
Creates a throttled function that only invokes the provided function at most once per every wait milliseconds
Use setTimeout() and clearTimeout() to throttle the given method, fn. Use Function.apply() to apply the this context to the function and provide the necessary arguments. Use Date.now() to keep track of the last time the throttled function was invoked. Omit the second argument, wait, to set the timeout at a default of 0 ms.
const throttle = (fn, wait) => {
   let inThrottle, lastFn, lastTime;
   return function() {
     const context = this,
@@ -262,14 +262,14 @@ document.body.log(window.innerHeight);
   }, 250)
 ); // Will log the window dimensions at most every 250ms
-
intermediate
times
Iterates over a callback n times
Use Function.call() to call fn n times or until it returns false. Omit the last argument, context, to use an undefined object (or the global object in non-strict mode).
const times = (n, fn, context = undefined) => {
+
times
Iterates over a callback n times
Use Function.call() to call fn n times or until it returns false. Omit the last argument, context, to use an undefined object (or the global object in non-strict mode).
const times = (n, fn, context = undefined) => {
   let i = 0;
   while (fn.call(context, i) !== false && ++i < n) {}
 };
 
var output = '';
 times(5, i => (output += i));
 console.log(output); // 01234
-
intermediate
uncurry
Uncurries a function up to depth n.
Return a variadic function. Use Array.reduce() on the provided arguments to call each subsequent curry level of the function. If the length of the provided arguments is less than n throw an error. Otherwise, call fn with the proper amount of arguments, using Array.slice(0, n). Omit the second argument, n, to uncurry up to depth 1.
const uncurry = (fn, n = 1) => (...args) => {
+
uncurry
Uncurries a function up to depth n.
Return a variadic function. Use Array.reduce() on the provided arguments to call each subsequent curry level of the function. If the length of the provided arguments is less than n throw an error. Otherwise, call fn with the proper amount of arguments, using Array.slice(0, n). Omit the second argument, n, to uncurry up to depth 1.
const uncurry = (fn, n = 1) => (...args) => {
   const next = acc => args => args.reduce((x, y) => x(y), acc);
   if (n > args.length) throw new RangeError('Arguments too few!');
   return next(fn)(args.slice(0, n));
@@ -277,7 +277,7 @@ console.log<
 
const add = x => y => z => x + y + z;
 const uncurriedAdd = uncurry(add, 3);
 uncurriedAdd(1, 2, 3); // 6
-
intermediate
unfold
Builds an array, using an iterator function and an initial seed value.
Use a while loop and Array.push() to call the function repeatedly until it returns false. The iterator function accepts one argument (seed) and must always return an array with two elements ([value, nextSeed]) or false to terminate.
const unfold = (fn, seed) => {
+
unfold
Builds an array, using an iterator function and an initial seed value.
Use a while loop and Array.push() to call the function repeatedly until it returns false. The iterator function accepts one argument (seed) and must always return an array with two elements ([value, nextSeed]) or false to terminate.
const unfold = (fn, seed) => {
   let result = [],
     val = [null, seed];
   while ((val = fn(val[1]))) result.push(val[0]);
@@ -285,8 +285,8 @@ console.log<
 };
 
var f = n => (n > 50 ? false : [-n, n + 10]);
 unfold(f, 10); // [-10, -20, -30, -40, -50]
-
intermediate
when
Tests a value, x, against a predicate function. If true, return fn(x). Else, return x.
Return a function expecting a single value, x, that returns the appropriate value based on pred.
const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x);
+
when
Tests a value, x, against a predicate function. If true, return fn(x). Else, return x.
Return a function expecting a single value, x, that returns the appropriate value based on pred.
const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x);
 
const doubleEvenNumbers = when(x => x % 2 === 0, x => x * 2);
 doubleEvenNumbers(2); // 4
 doubleEvenNumbers(1); // 1
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/glossary.html b/docs/glossary.html index 10eadea4e..e5d7ada81 100644 --- a/docs/glossary.html +++ b/docs/glossary.html @@ -73,4 +73,4 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Glossary

Developers use a lot of terminology daily. Every once in a while, you might find a term you do not know. We know how frustrating that can get, so we provide you with a handy glossary of frequently used web development terms.


AJAX

Asynchronous JavaScript and XML (known as AJAX) is a term that describes a new approach to using multiple technologies together in order to enable web applications to make quick updates to the user interface without reloading the entire browser page.

API

API stands for Application Programming Interface and is a set of features and rules provided by a provided by a software to enable third-party software to interact with it. The code features of a web API usually include methods, properties, events or URLs.

Argument

An argument is a value passed as an input to a function and can be either a primitive or an object. In JavaScript, functions can also be passed as arguments to other functions.

Array

Arrays are used to store multiple values in a single variable. Arrays are ordered and each item in an array has a numeric index associated with it. JavaScript arrays are zero-indexed, meaning the first element's index is 0.

Asynchronous programming

Asynchronous programming is a way to allow multiple events to trigger code without waiting for each other. The main benefits of asynchronous programming are improved application performance and responsiveness.

Automatic semicolon insertion

Automatic semicolon insertion (ASI) is a JavaScript feature that allows developers to omit semicolons in their code.

Boolean

Booleans are one of the primitive data types in JavaScript. They represent logical data values and can only be true or false.

Callback

A callback function, also known as a high-order function, is a function that is passed into another function as an argument, which is then executed inside the outer function. Callbacks can be synchronous or asynchronous.

Character encoding

A character encoding defines a mapping between bytes and text, specifying how the sequenece of bytes should be interpreted. Two commonly used character encodings are ASCII and UTF-8.

Class

In object-oriented programming, a class is a template definition of an object's properties and methods.

Closure

A closure is the combination of a function and the lexical environment within which that function was declared. The closure allows a function to access the contents of that environment.

CoffeeScript

CoffeeScript is a programming language inspired by Ruby, Python and Haskell that transpiles to JavaScript.

Constant

A constant is a value, associated with an identifier. The value of a constant can be accessed using the identifier and cannot be altered during execution.

Constructor

In class-based object-oriented programming, a constructor is a special type of function called to instantiate an object. Constructors often accept arguments that are commonly used to set member properties.

Continuous Deployment

Continuous Deployment follows the testing that happens during Continuous Integration and pushes changes to a staging or production system. Continuous Deployment ensures that a version of the codebase is accessible at all times.

Continuous Integration

Continuous Integration (CI) is the practice of testing each change done to a codebase automatically and as early as possible. Two popular CI systems that integrate with GitHub are Travis CI and Circle CI.

CORS

Cross-Origin Resource Sharing (known as CORS) is a mechanism that uses extra HTTP headers to tell a browser to let a web application running at one domain have permission to access resources from a server at a different domain.

Cross-site scripting (XSS)

XSS refers to client-side code injection where the attacker injects malicious scripts into a legitimate website or web application. This is often achieved when the application does not validate user input and freely injects dynamic HTML content.

CSS

CSS stands for Cascading Style Sheets and is a language used to style web pages. CSS documents are plaintext documents structured with rules, which consist of element selectors and property-value pairs that apply the styles to the specified selectors.

CSV

CSV stands for Comma-Separated Values and is a storage format for tabular data. CSV documents are plaintext documents where each line represents a table row, with table columns separated by commas or some other delimiter (e.g. semicolons). The first line of a CSV document sometimes consists of the table column headings for the data to follow.

Currying

Currying is a way of constructing functions that allows partial application of a function's arguments. Practically, this means that a function is broken down into a series of functions, each one accepting part of the arguments.

Deserialization

Deserialization is the process of converting a format that has been transferred over a network and/or used for storage to an object or data structure. A common type of deserialization in JavaScript is the conversion of JSON string into an object.

DNS

A DNS (Domain Name System) translates domain names to the IP addresses needed to find a particular computer service on a network.

DOM

The DOM (Document Object Model) is a cross-platform API that treats HTML and XML documents as a tree structure consisting of nodes. These nodes (such as elements and text nodes) are objects that can be programmatically manipulated and any visible changes made to them are reflected live in the document. In a browser, this API is available to JavaScript where DOM nodes can be manipulated to change their styles, contents, placement in the document, or interacted with through event listeners.

Domain name registrar

A domain name registrar is a company that manages the reservation of internet domain names. A domain name registrar must be approved by a general top-level domain (gTLD) registry or a country code top-level domain (ccTLD) registry.

Domain name

A domain name is a website's address on the Internet, used primarily in URLs to identify the server for each webpage. A domain name consists of a hierarchical sequence of names, separated by dots and ending with an extension.

Element

A JavaScript representation of a DOM element commonly returned by document.querySelector() and document.createElement(). They are used when creating content with JavaScript for display in the DOM that needs to be programatically generated.

ES6

ES6 stands for ECMAScript 6 (also known as ECMAScript 2015), a version of the ECMAScript specification that standardizes JavaScript. ES6 adds a wide variety of new features to the specification, such as classes, promises, generators and arrow functions.

Event-driven programming

Event-driven programming is a programming paradigm in which the flow of the program is determined by events (e.g. user actions, thread messages, sensor outputs). In event-driven applications, there is usually a main loop that listens for events and trigger callback functions accordingly when one of these events is detected.

Event loop

The event loop handles all asynchronous callbacks. Callbacks are queued in a loop, while other code runs, and will run one by one when the response for each one has been received. The event loop allows JavaScript to perform non-blocking I/O operations, despite the fact that JavaScript is single-threaded.

Express

Express is a backend framework, that provides a layer of fundamental web application features for Node.js. Some of its key features are routing, middleware, template engines and error handling.

Factory functions

In JavaScript, a factory function is any function, which is not a class or constructor, that returns a new object. Factory functions don't require the use of the new keyword.

First-class function

A programming language is said to have first-class functions if it treats them as first-class citizens, meaning they can be passed as arguments, be returned as values from other functions, be assigned to variables and stored in data structures.

Flexbox

Flexbox is a one-dimensional layout model used to style websites as a property that could advance space distribution between items and provide powerful alignment capabilities.

Function

Functions are self-contained blocks of code with their own scope, that can be called by other code and are usually associated with a unique identifier. Functions accept input in the form of arguments and can optionally return an output (if no return statement is present, the default value of undefined will be returned instead). JavaScript functions are also objects.

Functional programming

Functional programming is a paradigm in which programs are built in a declarative manner using pure functions that avoid shared state and mutable data. Functions that always return the same value for the same input and don't produce side effects are the pillar of functional programming.

Functor

A Functor is a data type common in functional programming that implements a map method. The map method takes a function and applies it to the data in the Functor, returning a new instance of the Functor with the result. JavaScript Arrays are an example of the Functor data type.

Garbage collection

Garbage collection is a form of automatic memory management. It attempts to reclaim memory occupied by objects that are no longer used by the program.

Git

Git is an open-source version control system, used for source code management. Git allows users to copy (clone) and edit code on their local machines, before merging it into the main code base (master repository).

Higher-order function

Higher-order functions are functions that either take other functions as arguments, return a function as a result, or both.

Hoisting

Hoisting is JavaScript's default behavior of adding declarations to memory during the compile phase. Hoisting allows for JavaScript variables to be used before the line they were declared on.

HTML

HTML stands for HyperText Markup Language and is a language used to structure web pages. HTML documents are plaintext documents structured with elements, which are surrounded by <> tags and optionally extended with attributes.

HTTP and HTTPS

The HyperText Transfer Protocol (HTTP) is the underlying network protocol that enables transfer of hypermedia documents on the Web, usually between a client and a server. The HyperText Transfer Protocol Secure (HTTPS) is an encrypted version of the HTTP protocol, that uses SSL to encrypt all data transfered between a client and a server.

Integer

Integers are one of the primitive data types in Javascript. They represent a numerical value that has no fractional component.

Integration testing

Integration testing is a type of software testing, used to test groups of units/components of a software. The purpose of integration tests are to validate that the units/components interact with each other as expected.

IP

An IP address is a number assigned to a device connected to a network that uses the Internet protocol. Two IP versions are currently in use - IPv4, the older version of the communication protocol (e.g. 192.168.1.100) and IPv6, the newest version of the communication protocol which allows for many different IP addresses (e.g. 0:0:0:0:ffff:c0a8:164).

jQuery

jQuery is a frontend JavaScript library, that simplifies DOM manipulation, AJAX calls and Event handling. jQuery uses its globally defined function, $(), to select and manipulate DOM elements.

JSON

JSON (JavaScript Object Notation) is a format for storing and exchanging data. It closely resembles the JavaScript object syntax, however some data types, such as dates and functions, cannot be natively represented and need to be serialized first.

ajax api argument array asynchronous-programming automatic-semicolon-insertion boolean callback character-encoding class closure coffeescript constant constructor continuous-deployment continuous-integration cors cross-site-scripting-xss css csv currying deserialization dns dom domain-name-registrar domain-name element es6 event-driven-programming event-loop express factory-functions first-class-function flexbox function functional-programming functor garbage-collection git higher-order-function hoisting html http-and-https integer integration-testing ip jquery json keyword_database mdn module mongodb mutabe-value mvc node-js nosql npm object-oriented-programming object prepared-statements promise prototype-based-programming pseudo-class pseudo-element pwa react readme recursion regular-expressions repository responsive-web-design scope selector seo serialization sql-injection sql ssl stream strict-mode string svg template-literals typescript unit-testing uri url utf-8 value-vs-reference variable viewport vue webassembly webgl webrtc websockets xhtml xml yarn

MDN

MDN Web Docs, formerly known as Mozilla Developer Network, is the official Mozilla website for development documentation of web standards and Mozilla projects.

Module

Modules are independent, self-contained pieces of code that can be incorporated into other pieces of code. Modules improve maintainability and reusability of the code.

MongoDB

MongoDB is a NoSQL database model that stores data in flexible, JSON-like documents, meaning fields can vary from document to document and data structure can be changed over time

Mutable value

Mutable value is a type of variable that can be changed once created. Objects are mutable as their state can be modified after they are created. Primitive values are not mutable as we perform reassignment once we change them.

MVC

MVC stands for Model-View-Controller and is a software design pattern, emphasizing separation of concerns (logic and display). The Model part of the MVC pattern refers to the data and business logic, the View handles the layout and display, while the Controller routes commands to the model and view parts.

Node.js

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. Node.js can execute JavaScript code outside of the browser and can be used to develop web backends or standalone applications.

NoSQL

NoSQL databases provide a mechanism to create, update, retrieve and calculate data that is stored in models that are non-tabular.

Npm

Npm is a package manager for the JavaScript programming language and the default package manager for Node.js. It consists of a command-line client and the npm registry, an online database of packages.

Object-oriented programming

Object-oriented programming (OOP) is a programming paradigm based on the concept of objects, which may contain both data and procedures which can be use to operate on them. JavaScript supports Object-oriented programming both via prototypes and classes.

Object

Objects are data structures that contain data and instructions for working with the data. Objects consist of key-value pairs, where the keys are alphanumeric identifiers and the values can either be primitives or objects. JavaScript functions are also objects.

Prepared statements

In databases management systems, prepared statements are templates that can be used to execute queries with the provided values substituting the template's parameters. Prepared statements offer many benefits, such as reusability, maintainability and higher security.

Promise

The Promise object represents the eventual completion (or failure) of an asynchronous operation, and its resulting value. A Promise can be in one of these states: pending(initial state, neither fulfilled nor rejected), fulfilled(operation completed successfully), rejected(operation failed).

Prototype-based programming

Prototype-based programming is a style of object-oriented programming, where inheritance is based on object delegation, reusing objects that serve as prototypes. Prototype-based programming allows the creation of objects before defining their classes.

Pseudo-class

In CSS, a pseudo-class is used to define a special state of an element and can be used as a selector in combination with an id, element or class selector.

Pseudo-element

In CSS, a pseudo-element is used to style specific parts of an element and can be used as a selector in combination with an id, element or class selector.

PWA

Progressive Web App (known as PWA) is a term used to describe web applications that load like regular websites but can offer the user functionality such as working offline, push notifications, and device hardware access that were traditionally available only to native mobile applications.

React

React is a frontend framework, that allows developers to create dynamic, component-based user interfaces. React separates view and state, utilizing a virtual DOM to update the user interface.

Recursion

Recursion is the repeated application of a process. In JavaScript, recursion involves functions that call themselves repeatedly until they reach a base condition. The base condition breaks out of the recursion loop because otherwise the function would call itself indefinitely. Recursion is very useful when working with nested data, especially when the nesting depth is dynamically defined or unkown.

Regular expressions

Regular expressions (known as regex or regexp) are patterns used to match character combinations in strings. JavaScript provides a regular expression implementation through the RegExp object.

Repository

In a version control system, a repository (or repo for short) is a data structure that stores metadata for a set of files (i.e. a project).

Responsive web design

Responsive web design is a web development concept aiming to provide optimal behavior and performance of websites on all web-enabled devices. Responsive web design is usually coupled with a mobile-first approach.

Scope

Each function has its own scope, and any variable declared within that function is only accessible from that function and any nested functions.

Selector

A CSS selector is a pattern that is used to select and/or style one or more elements in a document, based on certain rules. The order in which CSS selectors apply styles to elements is based on the rules of CSS specificity.

SEO

SEO stands for Search Engine Optimization and refers to the process of improving a website's search rankings and visibility.

Serialization

Serialization is the process of converting an object or data structure into a format suitable for transfer over a network and/or storage. A common type of serialization in JavaScript is the conversion of an object into a JSON string.

SQL injection

SQL injection is a code injection technique, used to attack data-driven applications. SQL injections get their name from the SQL language and mainly target data stored in relational databases.

SQL

SQL stands for Structured Query Language and is a language used to create, update, retrieve and calculate data in table-based databases. SQL databases use a relational database model and are particularly useful in handlind structured data with relations between different entities.

SSL

Secure Sockets Layer, commonly known as SSL or TLS, is a set of protocols and standards for transferring private data across the Internet. SSL uses a cryptographic system that uses two keys to encrypt data.

Stream

A stream is a sequence of data made available over time, often due to network transmission or storage access times.

Strict mode

JavaScript's strict mode is a JavaScript feature that allows developers to use a more restrictive variant of JavaScript and it can be enabled by adding 'use strict'; at the very top of their code. Strict mode elimiated some silent errors, might improve performance and changes the behavior of eval and arguments among other things.

String

Strings are one of the primitive data types in JavaScript. They are sequences of characters and are used to represent text.

SVG

SVG stands for Scalable Vector Graphics and is a 2D vector image format based on an XML syntax. SVG images can scale infinitely and can utilize clipping, masking, filters, animations etc.

Template literals

Template literals are strings that allow embedded expressions. They support multi-line strings, expression interpolation and nesting.

TypeScript

TypeScript is a superset of JavaScript, adding optional static typing to the language. TypeScript compiles to plain JavaScript.

Unit testing

Unit testing is a type of software testing, used to test individual units/components of a software. The purpose of unit tests are to validate that each individual unit/component performs as designed.

URI

URI stands for Uniform Resource Identifier and is a text string referring to a resource. A common type of URI is a URL, which is used for the identification of resources on the Web.

URL

URL stands for Uniform Resource Locator and is a text string specifying where a resource can be found on the Internet. In the HTTP protocol, URLs are the same as web addresses and hyperlinks.

UTF-8

UTF-8 stands for UCS Transformation Format 8 and is a commonly used character encoding. UTF-8 is backwards compatible with ASCII and can represent any standard Unicode character.

Value vs reference

When passing a variable by value, a copy of the variable is made, meaning that any changes made to the contents of the variable will not be reflected in the original variable. When passing a variable by reference, the memory address of the actual variable is passed to the function or variable, meaning that modifying the variable's contents will be reflected in the original variable. In JavaScript primitive data types are passed by value while objects are passed by reference.

Variable

A variable is a storage location, associated with an identifier and containing a value. The value of a variable can be referred using the identifier and can be altered during execution.

Viewport

A viewport is a polygonal (usually rectangular) area in computer graphics that is currently being viewed. In web development and design, it refers to the visible part of the document that is being viewed by the user in the browser window.

Vue

Vue.js is a progressive frontend framework for building user interfaces. Vue.js separates view and state, utilizing a virtual DOM to update the user interface.

WebAssembly

WebAssembly (WA) is a web standard that defines an assembly-like text format and corresponding binary format for executalbe code in web pages. WebAssembly is meant to complement JavaScript and improve its performance to match native code performance.

WebGL

WebGL stands for Web Graphics Library and is a JavaScript API that can be used for drawing interactive 2D and 3D graphics. WebGL is based on OpenGL and can be invoked within HTML <canvas> elements, which provide a rendering surface.

WebRTC

WebRTC stands for Web Real-Time Communication and is an API that can be used for video-chat, voice-calling and P2P-file-sharing web apps.

WebSockets

WebSockets is a protocol that allows for a persistent client-server TCP connection. The WebSocket protocol uses lower overheads, facilitating real-time data transfer between client and server.

XHTML

XHTML stands for EXtensible HyperText Markup Language and is a language used to structure web pages. XHTML is a reformulation of the HTML document structure as an application of XML.

XML

XML stands for eXtensible Markup Language and is a generic markup language specified by the W3C. XML documents are plaintext documents structured with user-defined tags, surrounded by <> and optionally extended with attributes.

Yarn

Yarn is a package manager made by Facebook. It can be used as an alternative to the npm package manager and is compatible with the public NPM registry.

\ No newline at end of file + }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Glossary

Developers use a lot of terminology daily. Every once in a while, you might find a term you do not know. We know how frustrating that can get, so we provide you with a handy glossary of frequently used web development terms.


AJAX

Asynchronous JavaScript and XML (known as AJAX) is a term that describes a new approach to using multiple technologies together in order to enable web applications to make quick updates to the user interface without reloading the entire browser page.

API

API stands for Application Programming Interface and is a set of features and rules provided by a provided by a software to enable third-party software to interact with it. The code features of a web API usually include methods, properties, events or URLs.

Argument

An argument is a value passed as an input to a function and can be either a primitive or an object. In JavaScript, functions can also be passed as arguments to other functions.

Array

Arrays are used to store multiple values in a single variable. Arrays are ordered and each item in an array has a numeric index associated with it. JavaScript arrays are zero-indexed, meaning the first element's index is 0.

Asynchronous programming

Asynchronous programming is a way to allow multiple events to trigger code without waiting for each other. The main benefits of asynchronous programming are improved application performance and responsiveness.

Automatic semicolon insertion

Automatic semicolon insertion (ASI) is a JavaScript feature that allows developers to omit semicolons in their code.

Boolean

Booleans are one of the primitive data types in JavaScript. They represent logical data values and can only be true or false.

Callback

A callback function, also known as a high-order function, is a function that is passed into another function as an argument, which is then executed inside the outer function. Callbacks can be synchronous or asynchronous.

Character encoding

A character encoding defines a mapping between bytes and text, specifying how the sequenece of bytes should be interpreted. Two commonly used character encodings are ASCII and UTF-8.

Class

In object-oriented programming, a class is a template definition of an object's properties and methods.

Closure

A closure is the combination of a function and the lexical environment within which that function was declared. The closure allows a function to access the contents of that environment.

CoffeeScript

CoffeeScript is a programming language inspired by Ruby, Python and Haskell that transpiles to JavaScript.

Constant

A constant is a value, associated with an identifier. The value of a constant can be accessed using the identifier and cannot be altered during execution.

Constructor

In class-based object-oriented programming, a constructor is a special type of function called to instantiate an object. Constructors often accept arguments that are commonly used to set member properties.

Continuous Deployment

Continuous Deployment follows the testing that happens during Continuous Integration and pushes changes to a staging or production system. Continuous Deployment ensures that a version of the codebase is accessible at all times.

Continuous Integration

Continuous Integration (CI) is the practice of testing each change done to a codebase automatically and as early as possible. Two popular CI systems that integrate with GitHub are Travis CI and Circle CI.

CORS

Cross-Origin Resource Sharing (known as CORS) is a mechanism that uses extra HTTP headers to tell a browser to let a web application running at one domain have permission to access resources from a server at a different domain.

Cross-site scripting (XSS)

XSS refers to client-side code injection where the attacker injects malicious scripts into a legitimate website or web application. This is often achieved when the application does not validate user input and freely injects dynamic HTML content.

CSS

CSS stands for Cascading Style Sheets and is a language used to style web pages. CSS documents are plaintext documents structured with rules, which consist of element selectors and property-value pairs that apply the styles to the specified selectors.

CSV

CSV stands for Comma-Separated Values and is a storage format for tabular data. CSV documents are plaintext documents where each line represents a table row, with table columns separated by commas or some other delimiter (e.g. semicolons). The first line of a CSV document sometimes consists of the table column headings for the data to follow.

Currying

Currying is a way of constructing functions that allows partial application of a function's arguments. Practically, this means that a function is broken down into a series of functions, each one accepting part of the arguments.

Deserialization

Deserialization is the process of converting a format that has been transferred over a network and/or used for storage to an object or data structure. A common type of deserialization in JavaScript is the conversion of JSON string into an object.

DNS

A DNS (Domain Name System) translates domain names to the IP addresses needed to find a particular computer service on a network.

DOM

The DOM (Document Object Model) is a cross-platform API that treats HTML and XML documents as a tree structure consisting of nodes. These nodes (such as elements and text nodes) are objects that can be programmatically manipulated and any visible changes made to them are reflected live in the document. In a browser, this API is available to JavaScript where DOM nodes can be manipulated to change their styles, contents, placement in the document, or interacted with through event listeners.

Domain name registrar

A domain name registrar is a company that manages the reservation of internet domain names. A domain name registrar must be approved by a general top-level domain (gTLD) registry or a country code top-level domain (ccTLD) registry.

Domain name

A domain name is a website's address on the Internet, used primarily in URLs to identify the server for each webpage. A domain name consists of a hierarchical sequence of names, separated by dots and ending with an extension.

Element

A JavaScript representation of a DOM element commonly returned by document.querySelector() and document.createElement(). They are used when creating content with JavaScript for display in the DOM that needs to be programatically generated.

ES6

ES6 stands for ECMAScript 6 (also known as ECMAScript 2015), a version of the ECMAScript specification that standardizes JavaScript. ES6 adds a wide variety of new features to the specification, such as classes, promises, generators and arrow functions.

Event-driven programming

Event-driven programming is a programming paradigm in which the flow of the program is determined by events (e.g. user actions, thread messages, sensor outputs). In event-driven applications, there is usually a main loop that listens for events and trigger callback functions accordingly when one of these events is detected.

Event loop

The event loop handles all asynchronous callbacks. Callbacks are queued in a loop, while other code runs, and will run one by one when the response for each one has been received. The event loop allows JavaScript to perform non-blocking I/O operations, despite the fact that JavaScript is single-threaded.

Express

Express is a backend framework, that provides a layer of fundamental web application features for Node.js. Some of its key features are routing, middleware, template engines and error handling.

Factory functions

In JavaScript, a factory function is any function, which is not a class or constructor, that returns a new object. Factory functions don't require the use of the new keyword.

First-class function

A programming language is said to have first-class functions if it treats them as first-class citizens, meaning they can be passed as arguments, be returned as values from other functions, be assigned to variables and stored in data structures.

Flexbox

Flexbox is a one-dimensional layout model used to style websites as a property that could advance space distribution between items and provide powerful alignment capabilities.

Function

Functions are self-contained blocks of code with their own scope, that can be called by other code and are usually associated with a unique identifier. Functions accept input in the form of arguments and can optionally return an output (if no return statement is present, the default value of undefined will be returned instead). JavaScript functions are also objects.

Functional programming

Functional programming is a paradigm in which programs are built in a declarative manner using pure functions that avoid shared state and mutable data. Functions that always return the same value for the same input and don't produce side effects are the pillar of functional programming.

Functor

A Functor is a data type common in functional programming that implements a map method. The map method takes a function and applies it to the data in the Functor, returning a new instance of the Functor with the result. JavaScript Arrays are an example of the Functor data type.

Garbage collection

Garbage collection is a form of automatic memory management. It attempts to reclaim memory occupied by objects that are no longer used by the program.

Git

Git is an open-source version control system, used for source code management. Git allows users to copy (clone) and edit code on their local machines, before merging it into the main code base (master repository).

Higher-order function

Higher-order functions are functions that either take other functions as arguments, return a function as a result, or both.

Hoisting

Hoisting is JavaScript's default behavior of adding declarations to memory during the compile phase. Hoisting allows for JavaScript variables to be used before the line they were declared on.

HTML

HTML stands for HyperText Markup Language and is a language used to structure web pages. HTML documents are plaintext documents structured with elements, which are surrounded by <> tags and optionally extended with attributes.

HTTP and HTTPS

The HyperText Transfer Protocol (HTTP) is the underlying network protocol that enables transfer of hypermedia documents on the Web, usually between a client and a server. The HyperText Transfer Protocol Secure (HTTPS) is an encrypted version of the HTTP protocol, that uses SSL to encrypt all data transfered between a client and a server.

Integer

Integers are one of the primitive data types in Javascript. They represent a numerical value that has no fractional component.

Integration testing

Integration testing is a type of software testing, used to test groups of units/components of a software. The purpose of integration tests are to validate that the units/components interact with each other as expected.

IP

An IP address is a number assigned to a device connected to a network that uses the Internet protocol. Two IP versions are currently in use - IPv4, the older version of the communication protocol (e.g. 192.168.1.100) and IPv6, the newest version of the communication protocol which allows for many different IP addresses (e.g. 0:0:0:0:ffff:c0a8:164).

jQuery

jQuery is a frontend JavaScript library, that simplifies DOM manipulation, AJAX calls and Event handling. jQuery uses its globally defined function, $(), to select and manipulate DOM elements.

JSON

JSON (JavaScript Object Notation) is a format for storing and exchanging data. It closely resembles the JavaScript object syntax, however some data types, such as dates and functions, cannot be natively represented and need to be serialized first.

ajax api argument array asynchronous-programming automatic-semicolon-insertion boolean callback character-encoding class closure coffeescript constant constructor continuous-deployment continuous-integration cors cross-site-scripting-xss css csv currying deserialization dns dom domain-name-registrar domain-name element es6 event-driven-programming event-loop express factory-functions first-class-function flexbox function functional-programming functor garbage-collection git higher-order-function hoisting html http-and-https integer integration-testing ip jquery json keyword_database mdn module mongodb mutabe-value mvc node-js nosql npm object-oriented-programming object prepared-statements promise prototype-based-programming pseudo-class pseudo-element pwa react readme recursion regular-expressions repository responsive-web-design scope selector seo serialization sql-injection sql ssl stream strict-mode string svg template-literals typescript unit-testing uri url utf-8 value-vs-reference variable viewport vue webassembly webgl webrtc websockets xhtml xml yarn

MDN

MDN Web Docs, formerly known as Mozilla Developer Network, is the official Mozilla website for development documentation of web standards and Mozilla projects.

Module

Modules are independent, self-contained pieces of code that can be incorporated into other pieces of code. Modules improve maintainability and reusability of the code.

MongoDB

MongoDB is a NoSQL database model that stores data in flexible, JSON-like documents, meaning fields can vary from document to document and data structure can be changed over time

Mutable value

Mutable value is a type of variable that can be changed once created. Objects are mutable as their state can be modified after they are created. Primitive values are not mutable as we perform reassignment once we change them.

MVC

MVC stands for Model-View-Controller and is a software design pattern, emphasizing separation of concerns (logic and display). The Model part of the MVC pattern refers to the data and business logic, the View handles the layout and display, while the Controller routes commands to the model and view parts.

Node.js

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. Node.js can execute JavaScript code outside of the browser and can be used to develop web backends or standalone applications.

NoSQL

NoSQL databases provide a mechanism to create, update, retrieve and calculate data that is stored in models that are non-tabular.

Npm

Npm is a package manager for the JavaScript programming language and the default package manager for Node.js. It consists of a command-line client and the npm registry, an online database of packages.

Object-oriented programming

Object-oriented programming (OOP) is a programming paradigm based on the concept of objects, which may contain both data and procedures which can be use to operate on them. JavaScript supports Object-oriented programming both via prototypes and classes.

Object

Objects are data structures that contain data and instructions for working with the data. Objects consist of key-value pairs, where the keys are alphanumeric identifiers and the values can either be primitives or objects. JavaScript functions are also objects.

Prepared statements

In databases management systems, prepared statements are templates that can be used to execute queries with the provided values substituting the template's parameters. Prepared statements offer many benefits, such as reusability, maintainability and higher security.

Promise

The Promise object represents the eventual completion (or failure) of an asynchronous operation, and its resulting value. A Promise can be in one of these states: pending(initial state, neither fulfilled nor rejected), fulfilled(operation completed successfully), rejected(operation failed).

Prototype-based programming

Prototype-based programming is a style of object-oriented programming, where inheritance is based on object delegation, reusing objects that serve as prototypes. Prototype-based programming allows the creation of objects before defining their classes.

Pseudo-class

In CSS, a pseudo-class is used to define a special state of an element and can be used as a selector in combination with an id, element or class selector.

Pseudo-element

In CSS, a pseudo-element is used to style specific parts of an element and can be used as a selector in combination with an id, element or class selector.

PWA

Progressive Web App (known as PWA) is a term used to describe web applications that load like regular websites but can offer the user functionality such as working offline, push notifications, and device hardware access that were traditionally available only to native mobile applications.

React

React is a frontend framework, that allows developers to create dynamic, component-based user interfaces. React separates view and state, utilizing a virtual DOM to update the user interface.

Recursion

Recursion is the repeated application of a process. In JavaScript, recursion involves functions that call themselves repeatedly until they reach a base condition. The base condition breaks out of the recursion loop because otherwise the function would call itself indefinitely. Recursion is very useful when working with nested data, especially when the nesting depth is dynamically defined or unkown.

Regular expressions

Regular expressions (known as regex or regexp) are patterns used to match character combinations in strings. JavaScript provides a regular expression implementation through the RegExp object.

Repository

In a version control system, a repository (or repo for short) is a data structure that stores metadata for a set of files (i.e. a project).

Responsive web design

Responsive web design is a web development concept aiming to provide optimal behavior and performance of websites on all web-enabled devices. Responsive web design is usually coupled with a mobile-first approach.

Scope

Each function has its own scope, and any variable declared within that function is only accessible from that function and any nested functions.

Selector

A CSS selector is a pattern that is used to select and/or style one or more elements in a document, based on certain rules. The order in which CSS selectors apply styles to elements is based on the rules of CSS specificity.

SEO

SEO stands for Search Engine Optimization and refers to the process of improving a website's search rankings and visibility.

Serialization

Serialization is the process of converting an object or data structure into a format suitable for transfer over a network and/or storage. A common type of serialization in JavaScript is the conversion of an object into a JSON string.

SQL injection

SQL injection is a code injection technique, used to attack data-driven applications. SQL injections get their name from the SQL language and mainly target data stored in relational databases.

SQL

SQL stands for Structured Query Language and is a language used to create, update, retrieve and calculate data in table-based databases. SQL databases use a relational database model and are particularly useful in handlind structured data with relations between different entities.

SSL

Secure Sockets Layer, commonly known as SSL or TLS, is a set of protocols and standards for transferring private data across the Internet. SSL uses a cryptographic system that uses two keys to encrypt data.

Stream

A stream is a sequence of data made available over time, often due to network transmission or storage access times.

Strict mode

JavaScript's strict mode is a JavaScript feature that allows developers to use a more restrictive variant of JavaScript and it can be enabled by adding 'use strict'; at the very top of their code. Strict mode elimiated some silent errors, might improve performance and changes the behavior of eval and arguments among other things.

String

Strings are one of the primitive data types in JavaScript. They are sequences of characters and are used to represent text.

SVG

SVG stands for Scalable Vector Graphics and is a 2D vector image format based on an XML syntax. SVG images can scale infinitely and can utilize clipping, masking, filters, animations etc.

Template literals

Template literals are strings that allow embedded expressions. They support multi-line strings, expression interpolation and nesting.

TypeScript

TypeScript is a superset of JavaScript, adding optional static typing to the language. TypeScript compiles to plain JavaScript.

Unit testing

Unit testing is a type of software testing, used to test individual units/components of a software. The purpose of unit tests are to validate that each individual unit/component performs as designed.

URI

URI stands for Uniform Resource Identifier and is a text string referring to a resource. A common type of URI is a URL, which is used for the identification of resources on the Web.

URL

URL stands for Uniform Resource Locator and is a text string specifying where a resource can be found on the Internet. In the HTTP protocol, URLs are the same as web addresses and hyperlinks.

UTF-8

UTF-8 stands for UCS Transformation Format 8 and is a commonly used character encoding. UTF-8 is backwards compatible with ASCII and can represent any standard Unicode character.

Value vs reference

When passing a variable by value, a copy of the variable is made, meaning that any changes made to the contents of the variable will not be reflected in the original variable. When passing a variable by reference, the memory address of the actual variable is passed to the function or variable, meaning that modifying the variable's contents will be reflected in the original variable. In JavaScript primitive data types are passed by value while objects are passed by reference.

Variable

A variable is a storage location, associated with an identifier and containing a value. The value of a variable can be referred using the identifier and can be altered during execution.

Viewport

A viewport is a polygonal (usually rectangular) area in computer graphics that is currently being viewed. In web development and design, it refers to the visible part of the document that is being viewed by the user in the browser window.

Vue

Vue.js is a progressive frontend framework for building user interfaces. Vue.js separates view and state, utilizing a virtual DOM to update the user interface.

WebAssembly

WebAssembly (WA) is a web standard that defines an assembly-like text format and corresponding binary format for executalbe code in web pages. WebAssembly is meant to complement JavaScript and improve its performance to match native code performance.

WebGL

WebGL stands for Web Graphics Library and is a JavaScript API that can be used for drawing interactive 2D and 3D graphics. WebGL is based on OpenGL and can be invoked within HTML <canvas> elements, which provide a rendering surface.

WebRTC

WebRTC stands for Web Real-Time Communication and is an API that can be used for video-chat, voice-calling and P2P-file-sharing web apps.

WebSockets

WebSockets is a protocol that allows for a persistent client-server TCP connection. The WebSocket protocol uses lower overheads, facilitating real-time data transfer between client and server.

XHTML

XHTML stands for EXtensible HyperText Markup Language and is a language used to structure web pages. XHTML is a reformulation of the HTML document structure as an application of XML.

XML

XML stands for eXtensible Markup Language and is a generic markup language specified by the W3C. XML documents are plaintext documents structured with user-defined tags, surrounded by <> and optionally extended with attributes.

Yarn

Yarn is a package manager made by Facebook. It can be used as an alternative to the npm package manager and is compatible with the public NPM registry.

\ No newline at end of file diff --git a/docs/index.html b/docs/index.html index 2057a85f1..341bc5ea9 100644 --- a/docs/index.html +++ b/docs/index.html @@ -73,79 +73,79 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Array

beginner

all

Returns true if the provided predicate function returns true for all elements in a collection, false otherwise.

Use Array.every() to test if all elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.

const all = (arr, fn = Boolean) => arr.every(fn);
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Array
all
Returns true if the provided predicate function returns true for all elements in a collection, false otherwise.
Use Array.every() to test if all elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.
const all = (arr, fn = Boolean) => arr.every(fn);
 
all([4, 2, 3], x => x > 1); // true
 all([1, 2, 3]); // true
-
beginner
allEqual
Check if all elements are equal
Use Array.every() to check if all the elements of the array are the same as the first one.
const allEqual = arr => arr.every(val => val === arr[0]);
+
allEqual
Check if all elements are equal
Use Array.every() to check if all the elements of the array are the same as the first one.
const allEqual = arr => arr.every(val => val === arr[0]);
 
allEqual([1, 2, 3, 4, 5, 6]); // false
 allEqual([1, 1, 1, 1]); // true
-
beginner
any
Returns true if the provided predicate function returns true for at least one element in a collection, false otherwise.
Use Array.some() to test if any elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.
const any = (arr, fn = Boolean) => arr.some(fn);
+
any
Returns true if the provided predicate function returns true for at least one element in a collection, false otherwise.
Use Array.some() to test if any elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.
const any = (arr, fn = Boolean) => arr.some(fn);
 
any([0, 1, 2, 0], x => x >= 2); // true
 any([0, 0, 1, 0]); // true
-
intermediate
arrayToCSV
Converts a 2D array to a comma-separated values (CSV) string.
Use Array.map() and Array.join(delimiter) to combine individual 1D arrays (rows) into strings. Use Array.join('\n') to combine all rows into a CSV string, separating each row with a newline. Omit the second argument, delimiter, to use a default delimiter of ,.
const arrayToCSV = (arr, delimiter = ',') =>
+
arrayToCSV
Converts a 2D array to a comma-separated values (CSV) string.
Use Array.map() and Array.join(delimiter) to combine individual 1D arrays (rows) into strings. Use Array.join('\n') to combine all rows into a CSV string, separating each row with a newline. Omit the second argument, delimiter, to use a default delimiter of ,.
const arrayToCSV = (arr, delimiter = ',') =>
   arr.map(v => v.map(x => `"${x}"`).join(delimiter)).join('\n');
 
arrayToCSV([['a', 'b'], ['c', 'd']]); // '"a","b"\n"c","d"'
 arrayToCSV([['a', 'b'], ['c', 'd']], ';'); // '"a";"b"\n"c";"d"'
-
intermediate
bifurcate
Splits values into two groups. If an element in filter is truthy, the corresponding element in the collection belongs to the first group; otherwise, it belongs to the second group.
Use Array.reduce() and Array.push() to add elements to groups, based on filter.
const bifurcate = (arr, filter) =>
+
bifurcate
Splits values into two groups. If an element in filter is truthy, the corresponding element in the collection belongs to the first group; otherwise, it belongs to the second group.
Use Array.reduce() and Array.push() to add elements to groups, based on filter.
const bifurcate = (arr, filter) =>
   arr.reduce((acc, val, i) => (acc[filter[i] ? 0 : 1].push(val), acc), [[], []]);
 
bifurcate(['beep', 'boop', 'foo', 'bar'], [true, true, false, true]); // [ ['beep', 'boop', 'bar'], ['foo'] ]
-
intermediate
bifurcateBy
Splits values into two groups according to a predicate function, which specifies which group an element in the input collection belongs to. If the predicate function returns a truthy value, the collection element belongs to the first group; otherwise, it belongs to the second group.
Use Array.reduce() and Array.push() to add elements to groups, based on the value returned by fn for each element.
const bifurcateBy = (arr, fn) =>
+
bifurcateBy
Splits values into two groups according to a predicate function, which specifies which group an element in the input collection belongs to. If the predicate function returns a truthy value, the collection element belongs to the first group; otherwise, it belongs to the second group.
Use Array.reduce() and Array.push() to add elements to groups, based on the value returned by fn for each element.
const bifurcateBy = (arr, fn) =>
   arr.reduce((acc, val, i) => (acc[fn(val, i) ? 0 : 1].push(val), acc), [[], []]);
 
bifurcateBy(['beep', 'boop', 'foo', 'bar'], x => x[0] === 'b'); // [ ['beep', 'boop', 'bar'], ['foo'] ]
-
intermediate
chunk
Chunks an array into smaller arrays of a specified size.
Use Array.from() to create a new array, that fits the number of chunks that will be produced. Use Array.slice() to map each element of the new array to a chunk the length of size. If the original array can't be split evenly, the final chunk will contain the remaining elements.
const chunk = (arr, size) =>
+
chunk
Chunks an array into smaller arrays of a specified size.
Use Array.from() to create a new array, that fits the number of chunks that will be produced. Use Array.slice() to map each element of the new array to a chunk the length of size. If the original array can't be split evenly, the final chunk will contain the remaining elements.
const chunk = (arr, size) =>
   Array.from({ length: Math.ceil(arr.length / size) }, (v, i) =>
     arr.slice(i * size, i * size + size)
   );
 
chunk([1, 2, 3, 4, 5], 2); // [[1,2],[3,4],[5]]
-
beginner
compact
Removes falsey values from an array.
Use Array.filter() to filter out falsey values (false, null, 0, "", undefined, and NaN).
const compact = arr => arr.filter(Boolean);
+
compact
Removes falsey values from an array.
Use Array.filter() to filter out falsey values (false, null, 0, "", undefined, and NaN).
const compact = arr => arr.filter(Boolean);
 
compact([0, 1, false, 2, '', 3, 'a', 'e' * 23, NaN, 's', 34]); // [ 1, 2, 3, 'a', 's', 34 ]
-
intermediate
countBy
Groups the elements of an array based on the given function and returns the count of elements in each group.
Use Array.map() to map the values of an array to a function or property name. Use Array.reduce() to create an object, where the keys are produced from the mapped results.
const countBy = (arr, fn) =>
+
countBy
Groups the elements of an array based on the given function and returns the count of elements in each group.
Use Array.map() to map the values of an array to a function or property name. Use Array.reduce() to create an object, where the keys are produced from the mapped results.
const countBy = (arr, fn) =>
   arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val, i) => {
     acc[val] = (acc[val] || 0) + 1;
     return acc;
   }, {});
 
countBy([6.1, 4.2, 6.3], Math.floor); // {4: 1, 6: 2}
 countBy(['one', 'two', 'three'], 'length'); // {3: 2, 5: 1}
-
intermediate
countOccurrences
Counts the occurrences of a value in an array.
Use Array.reduce() to increment a counter each time you encounter the specific value inside the array.
const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);
+
countOccurrences
Counts the occurrences of a value in an array.
Use Array.reduce() to increment a counter each time you encounter the specific value inside the array.
const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);
 
countOccurrences([1, 1, 2, 1, 2, 3], 1); // 3
-
intermediate
deepFlatten
Deep flattens an array.
Use recursion. Use Array.concat() with an empty array ([]) and the spread operator (...) to flatten an array. Recursively flatten each element that is an array.
const deepFlatten = arr => [].concat(...arr.map(v => (Array.isArray(v) ? deepFlatten(v) : v)));
+
deepFlatten
Deep flattens an array.
Use recursion. Use Array.concat() with an empty array ([]) and the spread operator (...) to flatten an array. Recursively flatten each element that is an array.
const deepFlatten = arr => [].concat(...arr.map(v => (Array.isArray(v) ? deepFlatten(v) : v)));
 
deepFlatten([1, [2], [[3], 4], 5]); // [1,2,3,4,5]
-
beginner
difference
Returns the difference between two arrays.
Create a Set from b, then use Array.filter() on a to only keep values not contained in b.
const difference = (a, b) => {
+
difference
Returns the difference between two arrays.
Create a Set from b, then use Array.filter() on a to only keep values not contained in b.
const difference = (a, b) => {
   const s = new Set(b);
   return a.filter(x => !s.has(x));
 };
 
difference([1, 2, 3], [1, 2, 4]); // [3]
-
intermediate
differenceBy
Returns the difference between two arrays, after applying the provided function to each array element of both.
Create a Set by applying fn to each element in b, then use Array.filter() in combination with fn on a to only keep values not contained in the previously created set.
const differenceBy = (a, b, fn) => {
+
differenceBy
Returns the difference between two arrays, after applying the provided function to each array element of both.
Create a Set by applying fn to each element in b, then use Array.filter() in combination with fn on a to only keep values not contained in the previously created set.
const differenceBy = (a, b, fn) => {
   const s = new Set(b.map(v => fn(v)));
   return a.filter(x => !s.has(fn(x)));
 };
 
differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1.2]
 differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [ { x: 2 } ]
-
intermediate
differenceWith
Filters out all values from an array for which the comparator function does not return true.
Use Array.filter() and Array.findIndex() to find the appropriate values.
const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
+
differenceWith
Filters out all values from an array for which the comparator function does not return true.
Use Array.filter() and Array.findIndex() to find the appropriate values.
const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
 
differenceWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0], (a, b) => Math.round(a) === Math.round(b)); // [1, 1.2]
-
beginner
drop
Returns a new array with n elements removed from the left.
Use Array.slice() to slice the remove the specified number of elements from the left.
const drop = (arr, n = 1) => arr.slice(n);
+
drop
Returns a new array with n elements removed from the left.
Use Array.slice() to slice the remove the specified number of elements from the left.
const drop = (arr, n = 1) => arr.slice(n);
 
drop([1, 2, 3]); // [2,3]
 drop([1, 2, 3], 2); // [3]
 drop([1, 2, 3], 42); // []
-
beginner
dropRight
Returns a new array with n elements removed from the right.
Use Array.slice() to slice the remove the specified number of elements from the right.
const dropRight = (arr, n = 1) => arr.slice(0, -n);
+
dropRight
Returns a new array with n elements removed from the right.
Use Array.slice() to slice the remove the specified number of elements from the right.
const dropRight = (arr, n = 1) => arr.slice(0, -n);
 
dropRight([1, 2, 3]); // [1,2]
 dropRight([1, 2, 3], 2); // [1]
 dropRight([1, 2, 3], 42); // []
-
intermediate
dropRightWhile
Removes elements from the end of an array until the passed function returns true. Returns the remaining elements in the array.
Loop through the array, using Array.slice() to drop the last element of the array until the returned value from the function is true. Returns the remaining elements.
const dropRightWhile = (arr, func) => {
+
dropRightWhile
Removes elements from the end of an array until the passed function returns true. Returns the remaining elements in the array.
Loop through the array, using Array.slice() to drop the last element of the array until the returned value from the function is true. Returns the remaining elements.
const dropRightWhile = (arr, func) => {
   while (arr.length > 0 && !func(arr[arr.length - 1])) arr = arr.slice(0, -1);
   return arr;
 };
 
dropRightWhile([1, 2, 3, 4], n => n < 3); // [1, 2]
-
intermediate
dropWhile
Removes elements in an array until the passed function returns true. Returns the remaining elements in the array.
Loop through the array, using Array.slice() to drop the first element of the array until the returned value from the function is true. Returns the remaining elements.
const dropWhile = (arr, func) => {
+
dropWhile
Removes elements in an array until the passed function returns true. Returns the remaining elements in the array.
Loop through the array, using Array.slice() to drop the first element of the array until the returned value from the function is true. Returns the remaining elements.
const dropWhile = (arr, func) => {
   while (arr.length > 0 && !func(arr[0])) arr = arr.slice(1);
   return arr;
 };
 
dropWhile([1, 2, 3, 4], n => n >= 3); // [3,4]
-
beginner
everyNth
Returns every nth element in an array.
Use Array.filter() to create a new array that contains every nth element of a given array.
const everyNth = (arr, nth) => arr.filter((e, i) => i % nth === nth - 1);
+
everyNth
Returns every nth element in an array.
Use Array.filter() to create a new array that contains every nth element of a given array.
const everyNth = (arr, nth) => arr.filter((e, i) => i % nth === nth - 1);
 
everyNth([1, 2, 3, 4, 5, 6], 2); // [ 2, 4, 6 ]
-
beginner
filterNonUnique
Filters out the non-unique values in an array.
Use Array.filter() for an array containing only the unique values.
const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));
+
filterNonUnique
Filters out the non-unique values in an array.
Use Array.filter() for an array containing only the unique values.
const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));
 
filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1,3,5]
-
intermediate
filterNonUniqueBy
Filters out the non-unique values in an array, based on a provided comparator function.
Use Array.filter() and Array.every() for an array containing only the unique values, based on the comparator function, fn. The comparator function takes four arguments: the values of the two elements being compared and their indexes.
const filterNonUniqueBy = (arr, fn) =>
+
filterNonUniqueBy
Filters out the non-unique values in an array, based on a provided comparator function.
Use Array.filter() and Array.every() for an array containing only the unique values, based on the comparator function, fn. The comparator function takes four arguments: the values of the two elements being compared and their indexes.
const filterNonUniqueBy = (arr, fn) =>
   arr.filter((v, i) => arr.every((x, j) => (i === j) === fn(v, x, i, j)));
 
filterNonUniqueBy(
   [
@@ -157,74 +157,74 @@
   ],
   (a, b) => a.id == b.id
 ); // [ { id: 2, value: 'c' } ]
-
beginner
findLast
Returns the last element for which the provided function returns a truthy value.
Use Array.filter() to remove elements for which fn returns falsey values, Array.pop() to get the last one.
const findLast = (arr, fn) => arr.filter(fn).pop();
+
findLast
Returns the last element for which the provided function returns a truthy value.
Use Array.filter() to remove elements for which fn returns falsey values, Array.pop() to get the last one.
const findLast = (arr, fn) => arr.filter(fn).pop();
 
findLast([1, 2, 3, 4], n => n % 2 === 1); // 3
-
intermediate
findLastIndex
Returns the index of the last element for which the provided function returns a truthy value.
Use Array.map() to map each element to an array with its index and value. Use Array.filter() to remove elements for which fn returns falsey values, Array.pop() to get the last one.
const findLastIndex = (arr, fn) =>
+
findLastIndex
Returns the index of the last element for which the provided function returns a truthy value.
Use Array.map() to map each element to an array with its index and value. Use Array.filter() to remove elements for which fn returns falsey values, Array.pop() to get the last one.
const findLastIndex = (arr, fn) =>
   arr
     .map((val, i) => [i, val])
     .filter(([i, val]) => fn(val, i, arr))
     .pop()[0];
 
findLastIndex([1, 2, 3, 4], n => n % 2 === 1); // 2 (index of the value 3)
-
intermediate
flatten
Flattens an array up to the specified depth.
Use recursion, decrementing depth by 1 for each level of depth. Use Array.reduce() and Array.concat() to merge elements or arrays. Base case, for depth equal to 1 stops recursion. Omit the second argument, depth to flatten only to a depth of 1 (single flatten).
const flatten = (arr, depth = 1) =>
+
flatten
Flattens an array up to the specified depth.
Use recursion, decrementing depth by 1 for each level of depth. Use Array.reduce() and Array.concat() to merge elements or arrays. Base case, for depth equal to 1 stops recursion. Omit the second argument, depth to flatten only to a depth of 1 (single flatten).
const flatten = (arr, depth = 1) =>
   arr.reduce((a, v) => a.concat(depth > 1 && Array.isArray(v) ? flatten(v, depth - 1) : v), []);
 
flatten([1, [2], 3, 4]); // [1, 2, 3, 4]
 flatten([1, [2, [3, [4, 5], 6], 7], 8], 2); // [1, 2, 3, [4, 5], 6, 7, 8]
-
intermediate
forEachRight
Executes a provided function once for each array element, starting from the array's last element.
Use Array.slice(0) to clone the given array, Array.reverse() to reverse it and Array.forEach() to iterate over the reversed array.
const forEachRight = (arr, callback) =>
+
forEachRight
Executes a provided function once for each array element, starting from the array's last element.
Use Array.slice(0) to clone the given array, Array.reverse() to reverse it and Array.forEach() to iterate over the reversed array.
const forEachRight = (arr, callback) =>
   arr
     .slice(0)
     .reverse()
     .forEach(callback);
 
forEachRight([1, 2, 3, 4], val => console.log(val)); // '4', '3', '2', '1'
-
intermediate
groupBy
Groups the elements of an array based on the given function.
Use Array.map() to map the values of an array to a function or property name. Use Array.reduce() to create an object, where the keys are produced from the mapped results.
const groupBy = (arr, fn) =>
+
groupBy
Groups the elements of an array based on the given function.
Use Array.map() to map the values of an array to a function or property name. Use Array.reduce() to create an object, where the keys are produced from the mapped results.
const groupBy = (arr, fn) =>
   arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val, i) => {
     acc[val] = (acc[val] || []).concat(arr[i]);
     return acc;
   }, {});
 
groupBy([6.1, 4.2, 6.3], Math.floor); // {4: [4.2], 6: [6.1, 6.3]}
 groupBy(['one', 'two', 'three'], 'length'); // {3: ['one', 'two'], 5: ['three']}
-
beginner
Returns the head of a list.
Use arr[0] to return the first element of the passed array.
const head = arr => arr[0];
+
Returns the head of a list.
Use arr[0] to return the first element of the passed array.
const head = arr => arr[0];
 
head([1, 2, 3]); // 1
-
intermediate
indexOfAll
Returns all indices of val in an array. If val never occurs, returns [].
Use Array.reduce() to loop over elements and store indices for matching elements. Return the array of indices.
const indexOfAll = (arr, val) => arr.reduce((acc, el, i) => (el === val ? [...acc, i] : acc), []);
+
indexOfAll
Returns all indices of val in an array. If val never occurs, returns [].
Use Array.reduce() to loop over elements and store indices for matching elements. Return the array of indices.
const indexOfAll = (arr, val) => arr.reduce((acc, el, i) => (el === val ? [...acc, i] : acc), []);
 
indexOfAll([1, 2, 3, 1, 2, 3], 1); // [0,3]
 indexOfAll([1, 2, 3], 4); // []
-
beginner
initial
Returns all the elements of an array except the last one.
Use arr.slice(0,-1) to return all but the last element of the array.
const initial = arr => arr.slice(0, -1);
+
initial
Returns all the elements of an array except the last one.
Use arr.slice(0,-1) to return all but the last element of the array.
const initial = arr => arr.slice(0, -1);
 
initial([1, 2, 3]); // [1,2]
-
intermediate
initialize2DArray
Initializes a 2D array of given width and height and value.
Use Array.map() to generate h rows where each is a new array of size w initialize with value. If the value is not provided, default to null.
const initialize2DArray = (w, h, val = null) =>
+
initialize2DArray
Initializes a 2D array of given width and height and value.
Use Array.map() to generate h rows where each is a new array of size w initialize with value. If the value is not provided, default to null.
const initialize2DArray = (w, h, val = null) =>
   Array.from({ length: h }).map(() => Array.from({ length: w }).fill(val));
 
initialize2DArray(2, 2, 0); // [[0,0], [0,0]]
-
intermediate
initializeArrayWithRange
Initializes an array containing the numbers in the specified range where start and end are inclusive with their common difference step.
Use Array.from() to create an array of the desired length, (end - start + 1)/step, and a map function to fill it with the desired values in the given range. You can omit start to use a default value of 0. You can omit step to use a default value of 1.
const initializeArrayWithRange = (end, start = 0, step = 1) =>
+
initializeArrayWithRange
Initializes an array containing the numbers in the specified range where start and end are inclusive with their common difference step.
Use Array.from() to create an array of the desired length, (end - start + 1)/step, and a map function to fill it with the desired values in the given range. You can omit start to use a default value of 0. You can omit step to use a default value of 1.
const initializeArrayWithRange = (end, start = 0, step = 1) =>
   Array.from({ length: Math.ceil((end - start + 1) / step) }, (v, i) => i * step + start);
 
initializeArrayWithRange(5); // [0,1,2,3,4,5]
 initializeArrayWithRange(7, 3); // [3,4,5,6,7]
 initializeArrayWithRange(9, 0, 2); // [0,2,4,6,8]
-
intermediate
initializeArrayWithRangeRight
Initializes an array containing the numbers in the specified range (in reverse) where start and end are inclusive with their common difference step.
Use Array.from(Math.ceil((end+1-start)/step)) to create an array of the desired length(the amounts of elements is equal to (end-start)/step or (end+1-start)/step for inclusive end), Array.map() to fill with the desired values in a range. You can omit start to use a default value of 0. You can omit step to use a default value of 1.
const initializeArrayWithRangeRight = (end, start = 0, step = 1) =>
+
initializeArrayWithRangeRight
Initializes an array containing the numbers in the specified range (in reverse) where start and end are inclusive with their common difference step.
Use Array.from(Math.ceil((end+1-start)/step)) to create an array of the desired length(the amounts of elements is equal to (end-start)/step or (end+1-start)/step for inclusive end), Array.map() to fill with the desired values in a range. You can omit start to use a default value of 0. You can omit step to use a default value of 1.
const initializeArrayWithRangeRight = (end, start = 0, step = 1) =>
   Array.from({ length: Math.ceil((end + 1 - start) / step) }).map(
     (v, i, arr) => (arr.length - i - 1) * step + start
   );
 
initializeArrayWithRangeRight(5); // [5,4,3,2,1,0]
 initializeArrayWithRangeRight(7, 3); // [7,6,5,4,3]
 initializeArrayWithRangeRight(9, 0, 2); // [8,6,4,2,0]
-
intermediate
initializeArrayWithValues
Initializes and fills an array with the specified values.
Use Array(n) to create an array of the desired length, fill(v) to fill it with the desired values. You can omit val to use a default value of 0.
const initializeArrayWithValues = (n, val = 0) => Array(n).fill(val);
+
initializeArrayWithValues
Initializes and fills an array with the specified values.
Use Array(n) to create an array of the desired length, fill(v) to fill it with the desired values. You can omit val to use a default value of 0.
const initializeArrayWithValues = (n, val = 0) => Array(n).fill(val);
 
initializeArrayWithValues(5, 2); // [2,2,2,2,2]
-
intermediate
initializeNDArray
Create a n-dimensional array with given value.
Use recursion. Use Array.map() to generate rows where each is a new array initialized using initializeNDArray.
const initializeNDArray = (val, ...args) =>
+
initializeNDArray
Create a n-dimensional array with given value.
Use recursion. Use Array.map() to generate rows where each is a new array initialized using initializeNDArray.
const initializeNDArray = (val, ...args) =>
   args.length === 0
     ? val
     : Array.from({ length: args[0] }).map(() => initializeNDArray(val, ...args.slice(1)));
 
initializeNDArray(1, 3); // [1,1,1]
 initializeNDArray(5, 2, 2, 2); // [[[5,5],[5,5]],[[5,5],[5,5]]]
-
intermediate
intersection
Returns a list of elements that exist in both arrays.
Create a Set from b, then use Array.filter() on a to only keep values contained in b.
const intersection = (a, b) => {
+
intersection
Returns a list of elements that exist in both arrays.
Create a Set from b, then use Array.filter() on a to only keep values contained in b.
const intersection = (a, b) => {
   const s = new Set(b);
   return a.filter(x => s.has(x));
 };
 
intersection([1, 2, 3], [4, 3, 2]); // [2,3]
-
intermediate
intersectionBy
Returns a list of elements that exist in both arrays, after applying the provided function to each array element of both.
Create a Set by applying fn to all elements in b, then use Array.filter() on a to only keep elements, which produce values contained in b when fn is applied to them.
const intersectionBy = (a, b, fn) => {
+
intersectionBy
Returns a list of elements that exist in both arrays, after applying the provided function to each array element of both.
Create a Set by applying fn to all elements in b, then use Array.filter() on a to only keep elements, which produce values contained in b when fn is applied to them.
const intersectionBy = (a, b, fn) => {
   const s = new Set(b.map(fn));
   return a.filter(x => s.has(fn(x)));
 };
 
intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [2.1]
-
intermediate
intersectionWith
Returns a list of elements that exist in both arrays, using a provided comparator function.
Use Array.filter() and Array.findIndex() in combination with the provided comparator to determine intersecting values.
const intersectionWith = (a, b, comp) => a.filter(x => b.findIndex(y => comp(x, y)) !== -1);
+
intersectionWith
Returns a list of elements that exist in both arrays, using a provided comparator function.
Use Array.filter() and Array.findIndex() in combination with the provided comparator to determine intersecting values.
const intersectionWith = (a, b, comp) => a.filter(x => b.findIndex(y => comp(x, y)) !== -1);
 
intersectionWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0, 3.9], (a, b) => Math.round(a) === Math.round(b)); // [1.5, 3, 0]
-
intermediate
isSorted
Returns 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted.
Calculate the ordering direction for the first two elements. Use Object.entries() to loop over array objects and compare them in pairs. Return 0 if the direction changes or the direction if the last element is reached.
const isSorted = arr => {
+
isSorted
Returns 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted.
Calculate the ordering direction for the first two elements. Use Object.entries() to loop over array objects and compare them in pairs. Return 0 if the direction changes or the direction if the last element is reached.
const isSorted = arr => {
   let direction = -(arr[0] - arr[1]);
   for (let [i, val] of arr.entries()) {
     direction = !direction ? -(arr[i - 1] - arr[i]) : direction;
@@ -235,7 +235,7 @@
 
isSorted([0, 1, 2, 2]); // 1
 isSorted([4, 3, 2]); // -1
 isSorted([4, 3, 5]); // 0
-
intermediate
join
Joins all elements of an array into a string and returns this string. Uses a separator and an end separator.
Use Array.reduce() to combine elements into a string. Omit the second argument, separator, to use a default separator of ','. Omit the third argument, end, to use the same value as separator by default.
const join = (arr, separator = ',', end = separator) =>
+
join
Joins all elements of an array into a string and returns this string. Uses a separator and an end separator.
Use Array.reduce() to combine elements into a string. Omit the second argument, separator, to use a default separator of ','. Omit the third argument, end, to use the same value as separator by default.
const join = (arr, separator = ',', end = separator) =>
   arr.reduce(
     (acc, val, i) =>
       i === arr.length - 2
@@ -248,7 +248,7 @@
 
join(['pen', 'pineapple', 'apple', 'pen'], ',', '&'); // "pen,pineapple,apple&pen"
 join(['pen', 'pineapple', 'apple', 'pen'], ','); // "pen,pineapple,apple,pen"
 join(['pen', 'pineapple', 'apple', 'pen']); // "pen,pineapple,apple,pen"
-
advanced
JSONtoCSV
Converts an array of objects to a comma-separated values (CSV) string that contains only the columns specified.
Use Array.join(demiliter) to combine all the names in columns to create the first row. Use Array.map() and Array.reduce() to create a row for each object, substituting non-existent values with empty strings and only mapping values in columns. Use Array.join('\n') to combine all rows into a string. Omit the third argument, delimiter, to use a default delimiter of ,.
const JSONtoCSV = (arr, columns, delimiter = ',') =>
+
JSONtoCSV
Converts an array of objects to a comma-separated values (CSV) string that contains only the columns specified.
Use Array.join(demiliter) to combine all the names in columns to create the first row. Use Array.map() and Array.reduce() to create a row for each object, substituting non-existent values with empty strings and only mapping values in columns. Use Array.join('\n') to combine all rows into a string. Omit the third argument, delimiter, to use a default delimiter of ,.
const JSONtoCSV = (arr, columns, delimiter = ',') =>
   [
     columns.join(delimiter),
     ...arr.map(obj =>
@@ -260,37 +260,37 @@
   ].join('\n');
 
JSONtoCSV([{ a: 1, b: 2 }, { a: 3, b: 4, c: 5 }, { a: 6 }, { b: 7 }], ['a', 'b']); // 'a,b\n"1","2"\n"3","4"\n"6",""\n"","7"'
 JSONtoCSV([{ a: 1, b: 2 }, { a: 3, b: 4, c: 5 }, { a: 6 }, { b: 7 }], ['a', 'b'], ';'); // 'a;b\n"1";"2"\n"3";"4"\n"6";""\n"";"7"'
-
beginner
last
Returns the last element in an array.
Use arr.length - 1 to compute the index of the last element of the given array and returning it.
const last = arr => arr[arr.length - 1];
+
last
Returns the last element in an array.
Use arr.length - 1 to compute the index of the last element of the given array and returning it.
const last = arr => arr[arr.length - 1];
 
last([1, 2, 3]); // 3
-
intermediate
longestItem
Takes any number of iterable objects or objects with a length property and returns the longest one. If multiple objects have the same length, the first one will be returned. Returns undefined if no arguments are provided.
Use Array.reduce(), comparing the length of objects to find the longest one.
const longestItem = (val, ...vals) =>
+
longestItem
Takes any number of iterable objects or objects with a length property and returns the longest one. If multiple objects have the same length, the first one will be returned. Returns undefined if no arguments are provided.
Use Array.reduce(), comparing the length of objects to find the longest one.
const longestItem = (val, ...vals) =>
   [val, ...vals].reduce((a, x) => (x.length > a.length ? x : a));
 
longestItem('this', 'is', 'a', 'testcase'); // 'testcase'
 longestItem(...['a', 'ab', 'abc']); // 'abc'
 longestItem(...['a', 'ab', 'abc'], 'abcd'); // 'abcd'
 longestItem([1, 2, 3], [1, 2], [1, 2, 3, 4, 5]); // [1, 2, 3, 4, 5]
 longestItem([1, 2, 3], 'foobar'); // 'foobar'
-
advanced
mapObject
Maps the values of an array to an object using a function, where the key-value pairs consist of the original value as the key and the mapped value.
Use an anonymous inner function scope to declare an undefined memory space, using closures to store a return value. Use a new Array to store the array with a map of the function over its data set and a comma operator to return a second step, without needing to move from one context to another (due to closures and order of operations).
const mapObject = (arr, fn) =>
+
mapObject
Maps the values of an array to an object using a function, where the key-value pairs consist of the original value as the key and the mapped value.
Use an anonymous inner function scope to declare an undefined memory space, using closures to store a return value. Use a new Array to store the array with a map of the function over its data set and a comma operator to return a second step, without needing to move from one context to another (due to closures and order of operations).
const mapObject = (arr, fn) =>
   (a => (
     (a = [arr, arr.map(fn)]), a[0].reduce((acc, val, ind) => ((acc[val] = a[1][ind]), acc), {})
   ))();
 
const squareIt = arr => mapObject(arr, a => a * a);
 squareIt([1, 2, 3]); // { 1: 1, 2: 4, 3: 9 }
-
beginner
maxN
Returns the n maximum elements from the provided array. If n is greater than or equal to the provided array's length, then return the original array(sorted in descending order).
Use Array.sort() combined with the spread operator (...) to create a shallow clone of the array and sort it in descending order. Use Array.slice() to get the specified number of elements. Omit the second argument, n, to get a one-element array.
const maxN = (arr, n = 1) => [...arr].sort((a, b) => b - a).slice(0, n);
+
maxN
Returns the n maximum elements from the provided array. If n is greater than or equal to the provided array's length, then return the original array(sorted in descending order).
Use Array.sort() combined with the spread operator (...) to create a shallow clone of the array and sort it in descending order. Use Array.slice() to get the specified number of elements. Omit the second argument, n, to get a one-element array.
const maxN = (arr, n = 1) => [...arr].sort((a, b) => b - a).slice(0, n);
 
maxN([1, 2, 3]); // [3]
 maxN([1, 2, 3], 2); // [3,2]
-
beginner
minN
Returns the n minimum elements from the provided array. If n is greater than or equal to the provided array's length, then return the original array(sorted in ascending order).
Use Array.sort() combined with the spread operator (...) to create a shallow clone of the array and sort it in ascending order. Use Array.slice() to get the specified number of elements. Omit the second argument, n, to get a one-element array.
const minN = (arr, n = 1) => [...arr].sort((a, b) => a - b).slice(0, n);
+
minN
Returns the n minimum elements from the provided array. If n is greater than or equal to the provided array's length, then return the original array(sorted in ascending order).
Use Array.sort() combined with the spread operator (...) to create a shallow clone of the array and sort it in ascending order. Use Array.slice() to get the specified number of elements. Omit the second argument, n, to get a one-element array.
const minN = (arr, n = 1) => [...arr].sort((a, b) => a - b).slice(0, n);
 
minN([1, 2, 3]); // [1]
 minN([1, 2, 3], 2); // [1,2]
-
beginner
none
Returns true if the provided predicate function returns false for all elements in a collection, false otherwise.
Use Array.some() to test if any elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.
const none = (arr, fn = Boolean) => !arr.some(fn);
+
none
Returns true if the provided predicate function returns false for all elements in a collection, false otherwise.
Use Array.some() to test if any elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.
const none = (arr, fn = Boolean) => !arr.some(fn);
 
none([0, 1, 3, 0], x => x == 2); // true
 none([0, 0, 0]); // true
-
beginner
nthElement
Returns the nth element of an array.
Use Array.slice() to get an array containing the nth element at the first place. If the index is out of bounds, return undefined. Omit the second argument, n, to get the first element of the array.
const nthElement = (arr, n = 0) => (n === -1 ? arr.slice(n) : arr.slice(n, n + 1))[0];
+
nthElement
Returns the nth element of an array.
Use Array.slice() to get an array containing the nth element at the first place. If the index is out of bounds, return undefined. Omit the second argument, n, to get the first element of the array.
const nthElement = (arr, n = 0) => (n === -1 ? arr.slice(n) : arr.slice(n, n + 1))[0];
 
nthElement(['a', 'b', 'c'], 1); // 'b'
 nthElement(['a', 'b', 'b'], -3); // 'a'
-
beginner
offset
Moves the specified amount of elements to the end of the array.
Use Array.slice() twice to get the elements after the specified index and the elements before that. Use the spread operator(...) to combine the two into one array. If offset is negative, the elements will be moved from end to start.
const offset = (arr, offset) => [...arr.slice(offset), ...arr.slice(0, offset)];
+
offset
Moves the specified amount of elements to the end of the array.
Use Array.slice() twice to get the elements after the specified index and the elements before that. Use the spread operator(...) to combine the two into one array. If offset is negative, the elements will be moved from end to start.
const offset = (arr, offset) => [...arr.slice(offset), ...arr.slice(0, offset)];
 
offset([1, 2, 3, 4, 5], 2); // [3, 4, 5, 1, 2]
 offset([1, 2, 3, 4, 5], -2); // [4, 5, 1, 2, 3]
-
intermediate
partition
Groups the elements into two arrays, depending on the provided function's truthiness for each element.
Use Array.reduce() to create an array of two arrays. Use Array.push() to add elements for which fn returns true to the first array and elements for which fn returns false to the second one.
const partition = (arr, fn) =>
+
partition
Groups the elements into two arrays, depending on the provided function's truthiness for each element.
Use Array.reduce() to create an array of two arrays. Use Array.push() to add elements for which fn returns true to the first array and elements for which fn returns false to the second one.
const partition = (arr, fn) =>
   arr.reduce(
     (acc, val, i, arr) => {
       acc[fn(val, i, arr) ? 0 : 1].push(val);
@@ -300,7 +300,7 @@
   );
 
const users = [{ user: 'barney', age: 36, active: false }, { user: 'fred', age: 40, active: true }];
 partition(users, o => o.active); // [[{ 'user': 'fred',    'age': 40, 'active': true }],[{ 'user': 'barney',  'age': 36, 'active': false }]]
-
advanced
permutations
⚠️ WARNING: This function's execution time increases exponentially with each array element. Anything more than 8 to 10 entries will cause your browser to hang as it tries to solve all the different combinations.
Generates all permutations of an array's elements (contains duplicates).
Use recursion. For each element in the given array, create all the partial permutations for the rest of its elements. Use Array.map() to combine the element with each partial permutation, then Array.reduce() to combine all permutations in one array. Base cases are for array length equal to 2 or 1.
const permutations = arr => {
+
permutations
⚠️ WARNING: This function's execution time increases exponentially with each array element. Anything more than 8 to 10 entries will cause your browser to hang as it tries to solve all the different combinations.
Generates all permutations of an array's elements (contains duplicates).
Use recursion. For each element in the given array, create all the partial permutations for the rest of its elements. Use Array.map() to combine the element with each partial permutation, then Array.reduce() to combine all permutations in one array. Base cases are for array length equal to 2 or 1.
const permutations = arr => {
   if (arr.length <= 2) return arr.length === 2 ? [arr, [arr[1], arr[0]]] : arr;
   return arr.reduce(
     (acc, item, i) =>
@@ -311,7 +311,7 @@
   );
 };
 
permutations([1, 33, 5]); // [ [ 1, 33, 5 ], [ 1, 5, 33 ], [ 33, 1, 5 ], [ 33, 5, 1 ], [ 5, 1, 33 ], [ 5, 33, 1 ] ]
-
intermediate
pull
Mutates the original array to filter out the values specified.
Use Array.filter() and Array.includes() to pull out the values that are not needed. Use Array.length = 0 to mutate the passed in an array by resetting it's length to zero and Array.push() to re-populate it with only the pulled values.
(For a snippet that does not mutate the original array see without)
const pull = (arr, ...args) => {
+
pull
Mutates the original array to filter out the values specified.
Use Array.filter() and Array.includes() to pull out the values that are not needed. Use Array.length = 0 to mutate the passed in an array by resetting it's length to zero and Array.push() to re-populate it with only the pulled values.
(For a snippet that does not mutate the original array see without)
const pull = (arr, ...args) => {
   let argState = Array.isArray(args[0]) ? args[0] : args;
   let pulled = arr.filter((v, i) => !argState.includes(v));
   arr.length = 0;
@@ -319,7 +319,7 @@
 };
 
let myArray = ['a', 'b', 'c', 'a', 'b', 'c'];
 pull(myArray, 'a', 'c'); // myArray = [ 'b', 'b' ]
-
advanced
pullAtIndex
Mutates the original array to filter out the values at the specified indexes.
Use Array.filter() and Array.includes() to pull out the values that are not needed. Use Array.length = 0 to mutate the passed in an array by resetting it's length to zero and Array.push() to re-populate it with only the pulled values. Use Array.push() to keep track of pulled values
const pullAtIndex = (arr, pullArr) => {
+
pullAtIndex
Mutates the original array to filter out the values at the specified indexes.
Use Array.filter() and Array.includes() to pull out the values that are not needed. Use Array.length = 0 to mutate the passed in an array by resetting it's length to zero and Array.push() to re-populate it with only the pulled values. Use Array.push() to keep track of pulled values
const pullAtIndex = (arr, pullArr) => {
   let removed = [];
   let pulled = arr
     .map((v, i) => (pullArr.includes(i) ? removed.push(v) : v))
@@ -330,7 +330,7 @@
 };
 
let myArray = ['a', 'b', 'c', 'd'];
 let pulled = pullAtIndex(myArray, [1, 3]); // myArray = [ 'a', 'c' ] , pulled = [ 'b', 'd' ]
-
advanced
pullAtValue
Mutates the original array to filter out the values specified. Returns the removed elements.
Use Array.filter() and Array.includes() to pull out the values that are not needed. Use Array.length = 0 to mutate the passed in an array by resetting it's length to zero and Array.push() to re-populate it with only the pulled values. Use Array.push() to keep track of pulled values
const pullAtValue = (arr, pullArr) => {
+
pullAtValue
Mutates the original array to filter out the values specified. Returns the removed elements.
Use Array.filter() and Array.includes() to pull out the values that are not needed. Use Array.length = 0 to mutate the passed in an array by resetting it's length to zero and Array.push() to re-populate it with only the pulled values. Use Array.push() to keep track of pulled values
const pullAtValue = (arr, pullArr) => {
   let removed = [],
     pushToRemove = arr.forEach((v, i) => (pullArr.includes(v) ? removed.push(v) : v)),
     mutateTo = arr.filter((v, i) => !pullArr.includes(v));
@@ -340,7 +340,7 @@
 };
 
let myArray = ['a', 'b', 'c', 'd'];
 let pulled = pullAtValue(myArray, ['b', 'd']); // myArray = [ 'a', 'c' ] , pulled = [ 'b', 'd' ]
-
advanced
pullBy
Mutates the original array to filter out the values specified, based on a given iterator function.
Check if the last argument provided in a function. Use Array.map() to apply the iterator function fn to all array elements. Use Array.filter() and Array.includes() to pull out the values that are not needed. Use Array.length = 0 to mutate the passed in an array by resetting it's length to zero and Array.push() to re-populate it with only the pulled values.
const pullBy = (arr, ...args) => {
+
pullBy
Mutates the original array to filter out the values specified, based on a given iterator function.
Check if the last argument provided in a function. Use Array.map() to apply the iterator function fn to all array elements. Use Array.filter() and Array.includes() to pull out the values that are not needed. Use Array.length = 0 to mutate the passed in an array by resetting it's length to zero and Array.push() to re-populate it with only the pulled values.
const pullBy = (arr, ...args) => {
   const length = args.length;
   let fn = length > 1 ? args[length - 1] : undefined;
   fn = typeof fn == 'function' ? (args.pop(), fn) : undefined;
@@ -351,7 +351,7 @@
 };
 
var myArray = [{ x: 1 }, { x: 2 }, { x: 3 }, { x: 1 }];
 pullBy(myArray, [{ x: 1 }, { x: 3 }], o => o.x); // myArray = [{ x: 2 }]
-
intermediate
reducedFilter
Filter an array of objects based on a condition while also filtering out unspecified keys.
Use Array.filter() to filter the array based on the predicate fn so that it returns the objects for which the condition returned a truthy value. On the filtered array, use Array.map() to return the new object using Array.reduce() to filter out the keys which were not supplied as the keys argument.
const reducedFilter = (data, keys, fn) =>
+
reducedFilter
Filter an array of objects based on a condition while also filtering out unspecified keys.
Use Array.filter() to filter the array based on the predicate fn so that it returns the objects for which the condition returned a truthy value. On the filtered array, use Array.map() to return the new object using Array.reduce() to filter out the keys which were not supplied as the keys argument.
const reducedFilter = (data, keys, fn) =>
   data.filter(fn).map(el =>
     keys.reduce((acc, key) => {
       acc[key] = el[key];
@@ -372,10 +372,10 @@
 ];
 
 reducedFilter(data, ['id', 'name'], item => item.age > 24); // [{ id: 2, name: 'mike'}]
-
intermediate
reduceSuccessive
Applies a function against an accumulator and each element in the array (from left to right), returning an array of successively reduced values.
Use Array.reduce() to apply the given function to the given array, storing each new result.
const reduceSuccessive = (arr, fn, acc) =>
+
reduceSuccessive
Applies a function against an accumulator and each element in the array (from left to right), returning an array of successively reduced values.
Use Array.reduce() to apply the given function to the given array, storing each new result.
const reduceSuccessive = (arr, fn, acc) =>
   arr.reduce((res, val, i, arr) => (res.push(fn(res.slice(-1)[0], val, i, arr)), res), [acc]);
 
reduceSuccessive([1, 2, 3, 4, 5, 6], (acc, val) => acc + val, 0); // [0, 1, 3, 6, 10, 15, 21]
-
intermediate
reduceWhich
Returns the minimum/maximum value of an array, after applying the provided function to set comparing rule.
Use Array.reduce() in combination with the comparator function to get the appropriate element in the array. You can omit the second parameter, comparator, to use the default one that returns the minimum element in the array.
const reduceWhich = (arr, comparator = (a, b) => a - b) =>
+
reduceWhich
Returns the minimum/maximum value of an array, after applying the provided function to set comparing rule.
Use Array.reduce() in combination with the comparator function to get the appropriate element in the array. You can omit the second parameter, comparator, to use the default one that returns the minimum element in the array.
const reduceWhich = (arr, comparator = (a, b) => a - b) =>
   arr.reduce((a, b) => (comparator(a, b) >= 0 ? b : a));
 
reduceWhich([1, 3, 2]); // 1
 reduceWhich([1, 3, 2], (a, b) => b - a); // 3
@@ -383,10 +383,10 @@
   [{ name: 'Tom', age: 12 }, { name: 'Jack', age: 18 }, { name: 'Lucy', age: 9 }],
   (a, b) => a.age - b.age
 ); // {name: "Lucy", age: 9}
-
beginner
reject
Takes a predicate and array, like Array.filter(), but only keeps x if pred(x) === false.
const reject = (pred, array) => array.filter((...args) => !pred(...args));
+
reject
Takes a predicate and array, like Array.filter(), but only keeps x if pred(x) === false.
const reject = (pred, array) => array.filter((...args) => !pred(...args));
 
reject(x => x % 2 === 0, [1, 2, 3, 4, 5]); // [1, 3, 5]
 reject(word => word.length > 4, ['Apple', 'Pear', 'Kiwi', 'Banana']); // ['Pear', 'Kiwi']
-
intermediate
remove
Removes elements from an array for which the given function returns false.
Use Array.filter() to find array elements that return truthy values and Array.reduce() to remove elements using Array.splice(). The func is invoked with three arguments (value, index, array).
const remove = (arr, func) =>
+
remove
Removes elements from an array for which the given function returns false.
Use Array.filter() to find array elements that return truthy values and Array.reduce() to remove elements using Array.splice(). The func is invoked with three arguments (value, index, array).
const remove = (arr, func) =>
   Array.isArray(arr)
     ? arr.filter(func).reduce((acc, val) => {
         arr.splice(arr.indexOf(val), 1);
@@ -394,9 +394,9 @@
       }, [])
     : [];
 
remove([1, 2, 3, 4], n => n % 2 === 0); // [2, 4]
-
beginner
sample
Returns a random element from an array.
Use Math.random() to generate a random number, multiply it by length and round it of to the nearest whole number using Math.floor(). This method also works with strings.
const sample = arr => arr[Math.floor(Math.random() * arr.length)];
+
sample
Returns a random element from an array.
Use Math.random() to generate a random number, multiply it by length and round it of to the nearest whole number using Math.floor(). This method also works with strings.
const sample = arr => arr[Math.floor(Math.random() * arr.length)];
 
sample([3, 7, 9, 11]); // 9
-
intermediate
sampleSize
Gets n random elements at unique keys from array up to the size of array.
Shuffle the array using the Fisher-Yates algorithm. Use Array.slice() to get the first n elements. Omit the second argument, n to get only one element at random from the array.
const sampleSize = ([...arr], n = 1) => {
+
sampleSize
Gets n random elements at unique keys from array up to the size of array.
Shuffle the array using the Fisher-Yates algorithm. Use Array.slice() to get the first n elements. Omit the second argument, n to get only one element at random from the array.
const sampleSize = ([...arr], n = 1) => {
   let m = arr.length;
   while (m) {
     const i = Math.floor(Math.random() * m--);
@@ -406,7 +406,7 @@
 };
 
sampleSize([1, 2, 3], 2); // [3,1]
 sampleSize([1, 2, 3], 4); // [2,3,1]
-
intermediate
shuffle
Randomizes the order of the values of an array, returning a new array.
Uses the Fisher-Yates algorithm to reorder the elements of the array.
const shuffle = ([...arr]) => {
+
shuffle
Randomizes the order of the values of an array, returning a new array.
Uses the Fisher-Yates algorithm to reorder the elements of the array.
const shuffle = ([...arr]) => {
   let m = arr.length;
   while (m) {
     const i = Math.floor(Math.random() * m--);
@@ -416,29 +416,29 @@
 };
 
const foo = [1, 2, 3];
 shuffle(foo); // [2,3,1], foo = [1,2,3]
-
beginner
similarity
Returns an array of elements that appear in both arrays.
Use Array.filter() to remove values that are not part of values, determined using Array.includes().
const similarity = (arr, values) => arr.filter(v => values.includes(v));
+
similarity
Returns an array of elements that appear in both arrays.
Use Array.filter() to remove values that are not part of values, determined using Array.includes().
const similarity = (arr, values) => arr.filter(v => values.includes(v));
 
similarity([1, 2, 3], [1, 2, 4]); // [1,2]
-
intermediate
sortedIndex
Returns the lowest index at which value should be inserted into array in order to maintain its sort order.
Check if the array is sorted in descending order (loosely). Use Array.findIndex() to find the appropriate index where the element should be inserted.
const sortedIndex = (arr, n) => {
+
sortedIndex
Returns the lowest index at which value should be inserted into array in order to maintain its sort order.
Check if the array is sorted in descending order (loosely). Use Array.findIndex() to find the appropriate index where the element should be inserted.
const sortedIndex = (arr, n) => {
   const isDescending = arr[0] > arr[arr.length - 1];
   const index = arr.findIndex(el => (isDescending ? n >= el : n <= el));
   return index === -1 ? arr.length : index;
 };
 
sortedIndex([5, 3, 2, 1], 4); // 1
 sortedIndex([30, 50], 40); // 1
-
intermediate
sortedIndexBy
Returns the lowest index at which value should be inserted into array in order to maintain its sort order, based on a provided iterator function.
Check if the array is sorted in descending order (loosely). Use Array.findIndex() to find the appropriate index where the element should be inserted, based on the iterator function fn.
const sortedIndexBy = (arr, n, fn) => {
+
sortedIndexBy
Returns the lowest index at which value should be inserted into array in order to maintain its sort order, based on a provided iterator function.
Check if the array is sorted in descending order (loosely). Use Array.findIndex() to find the appropriate index where the element should be inserted, based on the iterator function fn.
const sortedIndexBy = (arr, n, fn) => {
   const isDescending = fn(arr[0]) > fn(arr[arr.length - 1]);
   const val = fn(n);
   const index = arr.findIndex(el => (isDescending ? val >= fn(el) : val <= fn(el)));
   return index === -1 ? arr.length : index;
 };
 
sortedIndexBy([{ x: 4 }, { x: 5 }], { x: 4 }, o => o.x); // 0
-
intermediate
sortedLastIndex
Returns the highest index at which value should be inserted into array in order to maintain its sort order.
Check if the array is sorted in descending order (loosely). Use Array.reverse() and Array.findIndex() to find the appropriate last index where the element should be inserted.
const sortedLastIndex = (arr, n) => {
+
sortedLastIndex
Returns the highest index at which value should be inserted into array in order to maintain its sort order.
Check if the array is sorted in descending order (loosely). Use Array.reverse() and Array.findIndex() to find the appropriate last index where the element should be inserted.
const sortedLastIndex = (arr, n) => {
   const isDescending = arr[0] > arr[arr.length - 1];
   const index = arr.reverse().findIndex(el => (isDescending ? n <= el : n >= el));
   return index === -1 ? 0 : arr.length - index;
 };
 
sortedLastIndex([10, 20, 30, 30, 40], 30); // 4
-
intermediate
sortedLastIndexBy
Returns the highest index at which value should be inserted into array in order to maintain its sort order, based on a provided iterator function.
Check if the array is sorted in descending order (loosely). Use Array.map() to apply the iterator function to all elements of the array. Use Array.reverse() and Array.findIndex() to find the appropriate last index where the element should be inserted, based on the provided iterator function.
const sortedLastIndexBy = (arr, n, fn) => {
+
sortedLastIndexBy
Returns the highest index at which value should be inserted into array in order to maintain its sort order, based on a provided iterator function.
Check if the array is sorted in descending order (loosely). Use Array.map() to apply the iterator function to all elements of the array. Use Array.reverse() and Array.findIndex() to find the appropriate last index where the element should be inserted, based on the provided iterator function.
const sortedLastIndexBy = (arr, n, fn) => {
   const isDescending = fn(arr[0]) > fn(arr[arr.length - 1]);
   const val = fn(n);
   const index = arr
@@ -448,27 +448,27 @@
   return index === -1 ? 0 : arr.length - index;
 };
 
sortedLastIndexBy([{ x: 4 }, { x: 5 }], { x: 4 }, o => o.x); // 1
-
advanced
stableSort
Performs stable sorting of an array, preserving the initial indexes of items when their values are the same. Does not mutate the original array, but returns a new array instead.
Use Array.map() to pair each element of the input array with its corresponding index. Use Array.sort() and a compare function to sort the list, preserving their initial order if the items compared are equal. Use Array.map() to convert back to the initial array items.
const stableSort = (arr, compare) =>
+
stableSort
Performs stable sorting of an array, preserving the initial indexes of items when their values are the same. Does not mutate the original array, but returns a new array instead.
Use Array.map() to pair each element of the input array with its corresponding index. Use Array.sort() and a compare function to sort the list, preserving their initial order if the items compared are equal. Use Array.map() to convert back to the initial array items.
const stableSort = (arr, compare) =>
   arr
     .map((item, index) => ({ item, index }))
     .sort((a, b) => compare(a.item, b.item) || a.index - b.index)
     .map(({ item }) => item);
 
const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
 const stable = stableSort(arr, () => 0); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
-
intermediate
symmetricDifference
Returns the symmetric difference between two arrays, without filtering out duplicate values.
Create a Set from each array, then use Array.filter() on each of them to only keep values not contained in the other.
const symmetricDifference = (a, b) => {
+
symmetricDifference
Returns the symmetric difference between two arrays, without filtering out duplicate values.
Create a Set from each array, then use Array.filter() on each of them to only keep values not contained in the other.
const symmetricDifference = (a, b) => {
   const sA = new Set(a),
     sB = new Set(b);
   return [...a.filter(x => !sB.has(x)), ...b.filter(x => !sA.has(x))];
 };
 
symmetricDifference([1, 2, 3], [1, 2, 4]); // [3, 4]
 symmetricDifference([1, 2, 2], [1, 3, 1]); // [2, 2, 3]
-
intermediate
symmetricDifferenceBy
Returns the symmetric difference between two arrays, after applying the provided function to each array element of both.
Create a Set by applying fn to each array's elements, then use Array.filter() on each of them to only keep values not contained in the other.
const symmetricDifferenceBy = (a, b, fn) => {
+
symmetricDifferenceBy
Returns the symmetric difference between two arrays, after applying the provided function to each array element of both.
Create a Set by applying fn to each array's elements, then use Array.filter() on each of them to only keep values not contained in the other.
const symmetricDifferenceBy = (a, b, fn) => {
   const sA = new Set(a.map(v => fn(v))),
     sB = new Set(b.map(v => fn(v)));
   return [...a.filter(x => !sB.has(fn(x))), ...b.filter(x => !sA.has(fn(x)))];
 };
 
symmetricDifferenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [ 1.2, 3.4 ]
-
intermediate
symmetricDifferenceWith
Returns the symmetric difference between two arrays, using a provided function as a comparator.
Use Array.filter() and Array.findIndex() to find the appropriate values.
const symmetricDifferenceWith = (arr, val, comp) => [
+
symmetricDifferenceWith
Returns the symmetric difference between two arrays, using a provided function as a comparator.
Use Array.filter() and Array.findIndex() to find the appropriate values.
const symmetricDifferenceWith = (arr, val, comp) => [
   ...arr.filter(a => val.findIndex(b => comp(a, b)) === -1),
   ...val.filter(a => arr.findIndex(b => comp(a, b)) === -1)
 ];
@@ -477,27 +477,27 @@
   [1.9, 3, 0, 3.9],
   (a, b) => Math.round(a) === Math.round(b)
 ); // [1, 1.2, 3.9]
-
beginner
tail
Returns all elements in an array except for the first one.
Return Array.slice(1) if the array's length is more than 1, otherwise, return the whole array.
const tail = arr => (arr.length > 1 ? arr.slice(1) : arr);
+
tail
Returns all elements in an array except for the first one.
Return Array.slice(1) if the array's length is more than 1, otherwise, return the whole array.
const tail = arr => (arr.length > 1 ? arr.slice(1) : arr);
 
tail([1, 2, 3]); // [2,3]
 tail([1]); // [1]
-
beginner
take
Returns an array with n elements removed from the beginning.
Use Array.slice() to create a slice of the array with n elements taken from the beginning.
const take = (arr, n = 1) => arr.slice(0, n);
+
take
Returns an array with n elements removed from the beginning.
Use Array.slice() to create a slice of the array with n elements taken from the beginning.
const take = (arr, n = 1) => arr.slice(0, n);
 
take([1, 2, 3], 5); // [1, 2, 3]
 take([1, 2, 3], 0); // []
-
intermediate
takeRight
Returns an array with n elements removed from the end.
Use Array.slice() to create a slice of the array with n elements taken from the end.
const takeRight = (arr, n = 1) => arr.slice(arr.length - n, arr.length);
+
takeRight
Returns an array with n elements removed from the end.
Use Array.slice() to create a slice of the array with n elements taken from the end.
const takeRight = (arr, n = 1) => arr.slice(arr.length - n, arr.length);
 
takeRight([1, 2, 3], 2); // [ 2, 3 ]
 takeRight([1, 2, 3]); // [3]
-
intermediate
takeRightWhile
Removes elements from the end of an array until the passed function returns true. Returns the removed elements.
Loop through the array, using a for...of loop over Array.keys() until the returned value from the function is true. Return the removed elements, using Array.reverse() and Array.slice().
const takeRightWhile = (arr, func) => {
+
takeRightWhile
Removes elements from the end of an array until the passed function returns true. Returns the removed elements.
Loop through the array, using a for...of loop over Array.keys() until the returned value from the function is true. Return the removed elements, using Array.reverse() and Array.slice().
const takeRightWhile = (arr, func) => {
   for (let i of arr.reverse().keys())
     if (func(arr[i])) return arr.reverse().slice(arr.length - i, arr.length);
   return arr;
 };
 
takeRightWhile([1, 2, 3, 4], n => n < 3); // [3, 4]
-
intermediate
takeWhile
Removes elements in an array until the passed function returns true. Returns the removed elements.
Loop through the array, using a for...of loop over Array.entries() until the returned value from the function is true. Return the removed elements, using Array.slice().
const takeWhile = (arr, func) => {
+
takeWhile
Removes elements in an array until the passed function returns true. Returns the removed elements.
Loop through the array, using a for...of loop over Array.entries() until the returned value from the function is true. Return the removed elements, using Array.slice().
const takeWhile = (arr, func) => {
   for (const [i, val] of arr.entries()) if (func(val)) return arr.slice(0, i);
   return arr;
 };
 
takeWhile([1, 2, 3, 4], n => n >= 3); // [1, 2]
-
intermediate
toHash
Reduces a given Array-like into a value hash (keyed data store).
Given an Iterable or Array-like structure, call Array.prototype.reduce.call() on the provided object to step over it and return an Object, keyed by the reference value.
const toHash = (object, key) =>
+
toHash
Reduces a given Array-like into a value hash (keyed data store).
Given an Iterable or Array-like structure, call Array.prototype.reduce.call() on the provided object to step over it and return an Object, keyed by the reference value.
const toHash = (object, key) =>
   Array.prototype.reduce.call(
     object,
     (acc, data, index) => ((acc[!key ? index : data[key]] = data), acc),
@@ -516,19 +516,19 @@ managers.for
     }, toHash(users, 'id')))
 );
 managers; // [ { manager:1, employees: [ { id: 2, first: "Joe" }, { id: 3, first: "Moe" } ] } ]
-
beginner
union
Returns every element that exists in any of the two arrays once.
Create a Set with all values of a and b and convert to an array.
const union = (a, b) => Array.from(new Set([...a, ...b]));
+
union
Returns every element that exists in any of the two arrays once.
Create a Set with all values of a and b and convert to an array.
const union = (a, b) => Array.from(new Set([...a, ...b]));
 
union([1, 2, 3], [4, 3, 2]); // [1,2,3,4]
-
intermediate
unionBy
Returns every element that exists in any of the two arrays once, after applying the provided function to each array element of both.
Create a Set by applying all fn to all values of a. Create a Set from a and all elements in b whose value, after applying fn does not match a value in the previously created set. Return the last set converted to an array.
const unionBy = (a, b, fn) => {
+
unionBy
Returns every element that exists in any of the two arrays once, after applying the provided function to each array element of both.
Create a Set by applying all fn to all values of a. Create a Set from a and all elements in b whose value, after applying fn does not match a value in the previously created set. Return the last set converted to an array.
const unionBy = (a, b, fn) => {
   const s = new Set(a.map(v => fn(v)));
   return Array.from(new Set([...a, ...b.filter(x => !s.has(fn(x)))]));
 };
 
unionBy([2.1], [1.2, 2.3], Math.floor); // [2.1, 1.2]
-
intermediate
unionWith
Returns every element that exists in any of the two arrays once, using a provided comparator function.
Create a Set with all values of a and values in b for which the comparator finds no matches in a, using Array.findIndex().
const unionWith = (a, b, comp) =>
+
unionWith
Returns every element that exists in any of the two arrays once, using a provided comparator function.
Create a Set with all values of a and values in b for which the comparator finds no matches in a, using Array.findIndex().
const unionWith = (a, b, comp) =>
   Array.from(new Set([...a, ...b.filter(x => a.findIndex(y => comp(x, y)) === -1)]));
 
unionWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0, 3.9], (a, b) => Math.round(a) === Math.round(b)); // [1, 1.2, 1.5, 3, 0, 3.9]
-
beginner
uniqueElements
Returns all unique values of an array.
Use ES6 Set and the ...rest operator to discard all duplicated values.
const uniqueElements = arr => [...new Set(arr)];
+
uniqueElements
Returns all unique values of an array.
Use ES6 Set and the ...rest operator to discard all duplicated values.
const uniqueElements = arr => [...new Set(arr)];
 
uniqueElements([1, 2, 2, 3, 4, 4, 5]); // [1,2,3,4,5]
-
intermediate
uniqueElementsBy
Returns all unique values of an array, based on a provided comparator function.
Use Array.reduce() and Array.some() for an array containing only the first unique occurence of each value, based on the comparator function, fn. The comparator function takes two arguments: the values of the two elements being compared.
const uniqueElementsBy = (arr, fn) =>
+
uniqueElementsBy
Returns all unique values of an array, based on a provided comparator function.
Use Array.reduce() and Array.some() for an array containing only the first unique occurence of each value, based on the comparator function, fn. The comparator function takes two arguments: the values of the two elements being compared.
const uniqueElementsBy = (arr, fn) =>
   arr.reduce((acc, v) => {
     if (!acc.some(x => fn(v, x))) acc.push(v);
     return acc;
@@ -543,7 +543,7 @@ managers; //
   ],
   (a, b) => a.id == b.id
 ); // [ { id: 0, value: 'a' }, { id: 1, value: 'b' }, { id: 2, value: 'c' } ]
-
intermediate
uniqueElementsByRight
Returns all unique values of an array, based on a provided comparator function.
Use Array.reduce() and Array.some() for an array containing only the last unique occurence of each value, based on the comparator function, fn. The comparator function takes two arguments: the values of the two elements being compared.
const uniqueElementsByRight = (arr, fn) =>
+
uniqueElementsByRight
Returns all unique values of an array, based on a provided comparator function.
Use Array.reduce() and Array.some() for an array containing only the last unique occurence of each value, based on the comparator function, fn. The comparator function takes two arguments: the values of the two elements being compared.
const uniqueElementsByRight = (arr, fn) =>
   arr.reduceRight((acc, v) => {
     if (!acc.some(x => fn(v, x))) acc.push(v);
     return acc;
@@ -558,12 +558,12 @@ managers; //
   ],
   (a, b) => a.id == b.id
 ); // [ { id: 0, value: 'e' }, { id: 1, value: 'd' }, { id: 2, value: 'c' } ]
-
intermediate
uniqueSymmetricDifference
Returns the unique symmetric difference between two arrays, not containing duplicate values from either array.
Use Array.filter() and Array.includes() on each array to remove values contained in the other, then create a Set from the results, removing duplicate values.
const uniqueSymmetricDifference = (a, b) => [
+
uniqueSymmetricDifference
Returns the unique symmetric difference between two arrays, not containing duplicate values from either array.
Use Array.filter() and Array.includes() on each array to remove values contained in the other, then create a Set from the results, removing duplicate values.
const uniqueSymmetricDifference = (a, b) => [
   ...new Set([...a.filter(v => !b.includes(v)), ...b.filter(v => !a.includes(v))])
 ];
 
uniqueSymmetricDifference([1, 2, 3], [1, 2, 4]); // [3, 4]
 uniqueSymmetricDifference([1, 2, 2], [1, 3, 1]); // [2, 3]
-
intermediate
unzip
Creates an array of arrays, ungrouping the elements in an array produced by zip.
Use Math.max.apply() to get the longest subarray in the array, Array.map() to make each element an array. Use Array.reduce() and Array.forEach() to map grouped values to individual arrays.
const unzip = arr =>
+
unzip
Creates an array of arrays, ungrouping the elements in an array produced by zip.
Use Math.max.apply() to get the longest subarray in the array, Array.map() to make each element an array. Use Array.reduce() and Array.forEach() to map grouped values to individual arrays.
const unzip = arr =>
   arr.reduce(
     (acc, val) => (val.forEach((v, i) => acc[i].push(v)), acc),
     Array.from({
@@ -572,7 +572,7 @@ managers; //
   );
 
unzip([['a', 1, true], ['b', 2, false]]); //[['a', 'b'], [1, 2], [true, false]]
 unzip([['a', 1, true], ['b', 2]]); //[['a', 'b'], [1, 2], [true]]
-
advanced
unzipWith
Creates an array of elements, ungrouping the elements in an array produced by zip and applying the provided function.
Use Math.max.apply() to get the longest subarray in the array, Array.map() to make each element an array. Use Array.reduce() and Array.forEach() to map grouped values to individual arrays. Use Array.map() and the spread operator (...) to apply fn to each individual group of elements.
const unzipWith = (arr, fn) =>
+
unzipWith
Creates an array of elements, ungrouping the elements in an array produced by zip and applying the provided function.
Use Math.max.apply() to get the longest subarray in the array, Array.map() to make each element an array. Use Array.reduce() and Array.forEach() to map grouped values to individual arrays. Use Array.map() and the spread operator (...) to apply fn to each individual group of elements.
const unzipWith = (arr, fn) =>
   arr
     .reduce(
       (acc, val) => (val.forEach((v, i) => acc[i].push(v)), acc),
@@ -582,11 +582,11 @@ managers; //
     )
     .map(val => fn(...val));
 
unzipWith([[1, 10, 100], [2, 20, 200]], (...args) => args.reduce((acc, v) => acc + v, 0)); // [3, 30, 300]
-
beginner
without
Filters out the elements of an array, that have one of the specified values.
Use Array.filter() to create an array excluding(using !Array.includes()) all given values.
(For a snippet that mutates the original array see pull)
const without = (arr, ...args) => arr.filter(v => !args.includes(v));
+
without
Filters out the elements of an array, that have one of the specified values.
Use Array.filter() to create an array excluding(using !Array.includes()) all given values.
(For a snippet that mutates the original array see pull)
const without = (arr, ...args) => arr.filter(v => !args.includes(v));
 
without([2, 1, 2, 3], 1, 2); // [3]
-
intermediate
xProd
Creates a new array out of the two supplied by creating each possible pair from the arrays.
Use Array.reduce(), Array.map() and Array.concat() to produce every possible pair from the elements of the two arrays and save them in an array.
const xProd = (a, b) => a.reduce((acc, x) => acc.concat(b.map(y => [x, y])), []);
+
xProd
Creates a new array out of the two supplied by creating each possible pair from the arrays.
Use Array.reduce(), Array.map() and Array.concat() to produce every possible pair from the elements of the two arrays and save them in an array.
const xProd = (a, b) => a.reduce((acc, x) => acc.concat(b.map(y => [x, y])), []);
 
xProd([1, 2], ['a', 'b']); // [[1, 'a'], [1, 'b'], [2, 'a'], [2, 'b']]
-
intermediate
zip
Creates an array of elements, grouped based on the position in the original arrays.
Use Math.max.apply() to get the longest array in the arguments. Creates an array with that length as return value and use Array.from() with a map-function to create an array of grouped elements. If lengths of the argument-arrays vary, undefined is used where no value could be found.
const zip = (...arrays) => {
+
zip
Creates an array of elements, grouped based on the position in the original arrays.
Use Math.max.apply() to get the longest array in the arguments. Creates an array with that length as return value and use Array.from() with a map-function to create an array of grouped elements. If lengths of the argument-arrays vary, undefined is used where no value could be found.
const zip = (...arrays) => {
   const maxLength = Math.max(...arrays.map(x => x.length));
   return Array.from({ length: maxLength }).map((_, i) => {
     return Array.from({ length: arrays.length }, (_, k) => arrays[k][i]);
@@ -594,11 +594,11 @@ managers; //
 };
 
zip(['a', 'b'], [1, 2], [true, false]); // [['a', 1, true], ['b', 2, false]]
 zip(['a'], [1, 2], [true, false]); // [['a', 1, true], [undefined, 2, false]]
-
intermediate
zipObject
Given an array of valid property identifiers and an array of values, return an object associating the properties to the values.
Since an object can have undefined values but not undefined property pointers, the array of properties is used to decide the structure of the resulting object using Array.reduce().
const zipObject = (props, values) =>
+
zipObject
Given an array of valid property identifiers and an array of values, return an object associating the properties to the values.
Since an object can have undefined values but not undefined property pointers, the array of properties is used to decide the structure of the resulting object using Array.reduce().
const zipObject = (props, values) =>
   props.reduce((obj, prop, index) => ((obj[prop] = values[index]), obj), {});
 
zipObject(['a', 'b', 'c'], [1, 2]); // {a: 1, b: 2, c: undefined}
 zipObject(['a', 'b'], [1, 2, 3]); // {a: 1, b: 2}
-
advanced
zipWith
Creates an array of elements, grouped based on the position in the original arrays and using function as the last value to specify how grouped values should be combined.
Check if the last argument provided is a function. Use Math.max() to get the longest array in the arguments. Creates an array with that length as return value and use Array.from() with a map-function to create an array of grouped elements. If lengths of the argument-arrays vary, undefined is used where no value could be found. The function is invoked with the elements of each group (...group).
const zipWith = (...array) => {
+
zipWith
Creates an array of elements, grouped based on the position in the original arrays and using function as the last value to specify how grouped values should be combined.
Check if the last argument provided is a function. Use Math.max() to get the longest array in the arguments. Creates an array with that length as return value and use Array.from() with a map-function to create an array of grouped elements. If lengths of the argument-arrays vary, undefined is used where no value could be found. The function is invoked with the elements of each group (...group).
const zipWith = (...array) => {
   const fn = typeof array[array.length - 1] === 'function' ? array.pop() : undefined;
   return Array.from(
     { length: Math.max(...array.map(a => a.length)) },
@@ -612,4 +612,4 @@ managers; //
   [100, 200],
   (a, b, c) => (a != null ? a : 'a') + (b != null ? b : 'b') + (c != null ? c : 'c')
 ); // [111, 222, '3bc']
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/math.html b/docs/math.html index 64280419e..d44a65f38 100644 --- a/docs/math.html +++ b/docs/math.html @@ -73,17 +73,17 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Math

beginner

approximatelyEqual

Checks if two numbers are approximately equal to each other.

Use Math.abs() to compare the absolute difference of the two values to epsilon. Omit the third parameter, epsilon, to use a default value of 0.001.

const approximatelyEqual = (v1, v2, epsilon = 0.001) => Math.abs(v1 - v2) < epsilon;
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Math
approximatelyEqual
Checks if two numbers are approximately equal to each other.
Use Math.abs() to compare the absolute difference of the two values to epsilon. Omit the third parameter, epsilon, to use a default value of 0.001.
const approximatelyEqual = (v1, v2, epsilon = 0.001) => Math.abs(v1 - v2) < epsilon;
 
approximatelyEqual(Math.PI / 2.0, 1.5708); // true
-
beginner
average
Returns the average of two or more numbers.
Use Array.reduce() to add each value to an accumulator, initialized with a value of 0, divide by the length of the array.
const average = (...nums) => nums.reduce((acc, val) => acc + val, 0) / nums.length;
+
average
Returns the average of two or more numbers.
Use Array.reduce() to add each value to an accumulator, initialized with a value of 0, divide by the length of the array.
const average = (...nums) => nums.reduce((acc, val) => acc + val, 0) / nums.length;
 
average(...[1, 2, 3]); // 2
 average(1, 2, 3); // 2
-
intermediate
averageBy
Returns the average of an array, after mapping each element to a value using the provided function.
Use Array.map() to map each element to the value returned by fn, Array.reduce() to add each value to an accumulator, initialized with a value of 0, divide by the length of the array.
const averageBy = (arr, fn) =>
+
averageBy
Returns the average of an array, after mapping each element to a value using the provided function.
Use Array.map() to map each element to the value returned by fn, Array.reduce() to add each value to an accumulator, initialized with a value of 0, divide by the length of the array.
const averageBy = (arr, fn) =>
   arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => acc + val, 0) /
   arr.length;
 
averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 5
 averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 5
-
intermediate
binomialCoefficient
Evaluates the binomial coefficient of two integers n and k.
Use Number.isNaN() to check if any of the two values is NaN. Check if k is less than 0, greater than or equal to n, equal to 1 or n - 1 and return the appropriate result. Check if n - k is less than k and switch their values accordingly. Loop from 2 through k and calculate the binomial coefficient. Use Math.round() to account for rounding errors in the calculation.
const binomialCoefficient = (n, k) => {
+
binomialCoefficient
Evaluates the binomial coefficient of two integers n and k.
Use Number.isNaN() to check if any of the two values is NaN. Check if k is less than 0, greater than or equal to n, equal to 1 or n - 1 and return the appropriate result. Check if n - k is less than k and switch their values accordingly. Loop from 2 through k and calculate the binomial coefficient. Use Math.round() to account for rounding errors in the calculation.
const binomialCoefficient = (n, k) => {
   if (Number.isNaN(n) || Number.isNaN(k)) return NaN;
   if (k < 0 || k > n) return 0;
   if (k === 0 || k === n) return 1;
@@ -94,16 +94,16 @@
   return Math.round(res);
 };
 
binomialCoefficient(8, 2); // 28
-
beginner
clampNumber
Clamps num within the inclusive range specified by the boundary values a and b.
If num falls within the range, return num. Otherwise, return the nearest number in the range.
const clampNumber = (num, a, b) => Math.max(Math.min(num, Math.max(a, b)), Math.min(a, b));
+
clampNumber
Clamps num within the inclusive range specified by the boundary values a and b.
If num falls within the range, return num. Otherwise, return the nearest number in the range.
const clampNumber = (num, a, b) => Math.max(Math.min(num, Math.max(a, b)), Math.min(a, b));
 
clampNumber(2, 3, 5); // 3
 clampNumber(1, -1, -5); // -1
-
beginner
degreesToRads
Converts an angle from degrees to radians.
Use Math.PI and the degree to radian formula to convert the angle from degrees to radians.
const degreesToRads = deg => (deg * Math.PI) / 180.0;
+
degreesToRads
Converts an angle from degrees to radians.
Use Math.PI and the degree to radian formula to convert the angle from degrees to radians.
const degreesToRads = deg => (deg * Math.PI) / 180.0;
 
degreesToRads(90.0); // ~1.5708
-
beginner
digitize
Converts a number to an array of digits.
Convert the number to a string, using the spread operator (...) to build an array. Use Array.map() and parseInt() to transform each value to an integer.
const digitize = n => [...`${n}`].map(i => parseInt(i));
+
digitize
Converts a number to an array of digits.
Convert the number to a string, using the spread operator (...) to build an array. Use Array.map() and parseInt() to transform each value to an integer.
const digitize = n => [...`${n}`].map(i => parseInt(i));
 
digitize(123); // [1, 2, 3]
-
beginner
distance
Returns the distance between two points.
Use Math.hypot() to calculate the Euclidean distance between two points.
const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0);
+
distance
Returns the distance between two points.
Use Math.hypot() to calculate the Euclidean distance between two points.
const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0);
 
distance(1, 1, 2, 3); // 2.23606797749979
-
advanced
elo
Computes the new ratings between two or more opponents using the Elo rating system. It takes an array of pre-ratings and returns an array containing post-ratings. The array should be ordered from best performer to worst performer (winner -> loser).
Use the exponent ** operator and math operators to compute the expected score (chance of winning). of each opponent and compute the new rating for each. Loop through the ratings, using each permutation to compute the post-Elo rating for each player in a pairwise fashion. Omit the second argument to use the default kFactor of 32.
const elo = ([...ratings], kFactor = 32, selfRating) => {
+
elo
Computes the new ratings between two or more opponents using the Elo rating system. It takes an array of pre-ratings and returns an array containing post-ratings. The array should be ordered from best performer to worst performer (winner -> loser).
Use the exponent ** operator and math operators to compute the expected score (chance of winning). of each opponent and compute the new rating for each. Loop through the ratings, using each permutation to compute the post-Elo rating for each player in a pairwise fashion. Omit the second argument to use the default kFactor of 32.
const elo = ([...ratings], kFactor = 32, selfRating) => {
   const [a, b] = ratings;
   const expectedScore = (self, opponent) => 1 / (1 + 10 ** ((opponent - self) / 400));
   const newRating = (rating, i) =>
@@ -130,7 +130,7 @@ For teams, each rating can adjusted based on own team's average rating vs.
 average rating of opposing team, with the score being added to their
 own individual rating by supplying it as the third argument.
 */
-
beginner
factorial
Calculates the factorial of a number.
Use recursion. If n is less than or equal to 1, return 1. Otherwise, return the product of n and the factorial of n - 1. Throws an exception if n is a negative number.
const factorial = n =>
+
factorial
Calculates the factorial of a number.
Use recursion. If n is less than or equal to 1, return 1. Otherwise, return the product of n and the factorial of n - 1. Throws an exception if n is a negative number.
const factorial = n =>
   n < 0
     ? (() => {
         throw new TypeError('Negative numbers are not allowed!');
@@ -139,28 +139,28 @@ own individual rating by supplying it as the third argument.
       ? 1
       : n * factorial(n - 1);
 
factorial(6); // 720
-
beginner
fibonacci
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1). Use Array.reduce() to add values into the array, using the sum of the last two values, except for the first two.
const fibonacci = n =>
+
fibonacci
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1). Use Array.reduce() to add values into the array, using the sum of the last two values, except for the first two.
const fibonacci = n =>
   Array.from({ length: n }).reduce(
     (acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
     []
   );
 
fibonacci(6); // [0, 1, 1, 2, 3, 5]
-
beginner
gcd
Calculates the greatest common divisor between two or more numbers/arrays.
The inner _gcd function uses recursion. Base case is when y equals 0. In this case, return x. Otherwise, return the GCD of y and the remainder of the division x/y.
const gcd = (...arr) => {
+
gcd
Calculates the greatest common divisor between two or more numbers/arrays.
The inner _gcd function uses recursion. Base case is when y equals 0. In this case, return x. Otherwise, return the GCD of y and the remainder of the division x/y.
const gcd = (...arr) => {
   const _gcd = (x, y) => (!y ? x : gcd(y, x % y));
   return [...arr].reduce((a, b) => _gcd(a, b));
 };
 
gcd(8, 36); // 4
 gcd(...[12, 8, 32]); // 4
-
intermediate
geometricProgression
Initializes an array containing the numbers in the specified range where start and end are inclusive and the ratio between two terms is step. Returns an error if step equals 1.
Use Array.from(), Math.log() and Math.floor() to create an array of the desired length, Array.map() to fill with the desired values in a range. Omit the second argument, start, to use a default value of 1. Omit the third argument, step, to use a default value of 2.
const geometricProgression = (end, start = 1, step = 2) =>
+
geometricProgression
Initializes an array containing the numbers in the specified range where start and end are inclusive and the ratio between two terms is step. Returns an error if step equals 1.
Use Array.from(), Math.log() and Math.floor() to create an array of the desired length, Array.map() to fill with the desired values in a range. Omit the second argument, start, to use a default value of 1. Omit the third argument, step, to use a default value of 2.
const geometricProgression = (end, start = 1, step = 2) =>
   Array.from({ length: Math.floor(Math.log(end / start) / Math.log(step)) + 1 }).map(
     (v, i) => start * step ** i
   );
 
geometricProgression(256); // [1, 2, 4, 8, 16, 32, 64, 128, 256]
 geometricProgression(256, 3); // [3, 6, 12, 24, 48, 96, 192]
 geometricProgression(256, 1, 4); // [1, 4, 16, 64, 256]
-
beginner
hammingDistance
Calculates the Hamming distance between two values.
Use XOR operator (^) to find the bit difference between the two numbers, convert to a binary string using toString(2). Count and return the number of 1s in the string, using match(/1/g).
const hammingDistance = (num1, num2) => ((num1 ^ num2).toString(2).match(/1/g) || '').length;
+
hammingDistance
Calculates the Hamming distance between two values.
Use XOR operator (^) to find the bit difference between the two numbers, convert to a binary string using toString(2). Count and return the number of 1s in the string, using match(/1/g).
const hammingDistance = (num1, num2) => ((num1 ^ num2).toString(2).match(/1/g) || '').length;
 
hammingDistance(2, 3); // 1
-
beginner
inRange
Checks if the given number falls within the given range.
Use arithmetic comparison to check if the given number is in the specified range. If the second parameter, end, is not specified, the range is considered to be from 0 to start.
const inRange = (n, start, end = null) => {
+
inRange
Checks if the given number falls within the given range.
Use arithmetic comparison to check if the given number is in the specified range. If the second parameter, end, is not specified, the range is considered to be from 0 to start.
const inRange = (n, start, end = null) => {
   if (end && start > end) [end, start] = [start, end];
   return end == null ? n >= 0 && n < start : n >= start && n < end;
 };
@@ -168,24 +168,24 @@ own individual rating by supplying it as the third argument.
 inRange(3, 4); // true
 inRange(2, 3, 5); // false
 inRange(3, 2); // false
-
beginner
isDivisible
Checks if the first numeric argument is divisible by the second one.
Use the modulo operator (%) to check if the remainder is equal to 0.
const isDivisible = (dividend, divisor) => dividend % divisor === 0;
+
isDivisible
Checks if the first numeric argument is divisible by the second one.
Use the modulo operator (%) to check if the remainder is equal to 0.
const isDivisible = (dividend, divisor) => dividend % divisor === 0;
 
isDivisible(6, 3); // true
-
beginner
isEven
Returns true if the given number is even, false otherwise.
Checks whether a number is odd or even using the modulo (%) operator. Returns true if the number is even, false if the number is odd.
const isEven = num => num % 2 === 0;
+
isEven
Returns true if the given number is even, false otherwise.
Checks whether a number is odd or even using the modulo (%) operator. Returns true if the number is even, false if the number is odd.
const isEven = num => num % 2 === 0;
 
isEven(3); // false
-
beginner
isPrime
Checks if the provided integer is a prime number.
Check numbers from 2 to the square root of the given number. Return false if any of them divides the given number, else return true, unless the number is less than 2.
const isPrime = num => {
+
isPrime
Checks if the provided integer is a prime number.
Check numbers from 2 to the square root of the given number. Return false if any of them divides the given number, else return true, unless the number is less than 2.
const isPrime = num => {
   const boundary = Math.floor(Math.sqrt(num));
   for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
   return num >= 2;
 };
 
isPrime(11); // true
-
beginner
lcm
Returns the least common multiple of two or more numbers.
Use the greatest common divisor (GCD) formula and the fact that lcm(x,y) = x * y / gcd(x,y) to determine the least common multiple. The GCD formula uses recursion.
const lcm = (...arr) => {
+
lcm
Returns the least common multiple of two or more numbers.
Use the greatest common divisor (GCD) formula and the fact that lcm(x,y) = x * y / gcd(x,y) to determine the least common multiple. The GCD formula uses recursion.
const lcm = (...arr) => {
   const gcd = (x, y) => (!y ? x : gcd(y, x % y));
   const _lcm = (x, y) => (x * y) / gcd(x, y);
   return [...arr].reduce((a, b) => _lcm(a, b));
 };
 
lcm(12, 7); // 84
 lcm(...[1, 3, 4, 5]); // 60
-
advanced
luhnCheck
Implementation of the Luhn Algorithm used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers etc.
Use String.split(''), Array.reverse() and Array.map() in combination with parseInt() to obtain an array of digits. Use Array.splice(0,1) to obtain the last digit. Use Array.reduce() to implement the Luhn Algorithm. Return true if sum is divisible by 10, false otherwise.
const luhnCheck = num => {
+
luhnCheck
Implementation of the Luhn Algorithm used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers etc.
Use String.split(''), Array.reverse() and Array.map() in combination with parseInt() to obtain an array of digits. Use Array.splice(0,1) to obtain the last digit. Use Array.reduce() to implement the Luhn Algorithm. Return true if sum is divisible by 10, false otherwise.
const luhnCheck = num => {
   let arr = (num + '')
     .split('')
     .reverse()
@@ -198,24 +198,24 @@ own individual rating by supplying it as the third argument.
 
luhnCheck('4485275742308327'); // true
 luhnCheck(6011329933655299); //  false
 luhnCheck(123456789); // false
-
beginner
maxBy
Returns the maximum value of an array, after mapping each element to a value using the provided function.
Use Array.map() to map each element to the value returned by fn, Math.max() to get the maximum value.
const maxBy = (arr, fn) => Math.max(...arr.map(typeof fn === 'function' ? fn : val => val[fn]));
+
maxBy
Returns the maximum value of an array, after mapping each element to a value using the provided function.
Use Array.map() to map each element to the value returned by fn, Math.max() to get the maximum value.
const maxBy = (arr, fn) => Math.max(...arr.map(typeof fn === 'function' ? fn : val => val[fn]));
 
maxBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 8
 maxBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 8
-
intermediate
median
Returns the median of an array of numbers.
Find the middle of the array, use Array.sort() to sort the values. Return the number at the midpoint if length is odd, otherwise the average of the two middle numbers.
const median = arr => {
+
median
Returns the median of an array of numbers.
Find the middle of the array, use Array.sort() to sort the values. Return the number at the midpoint if length is odd, otherwise the average of the two middle numbers.
const median = arr => {
   const mid = Math.floor(arr.length / 2),
     nums = [...arr].sort((a, b) => a - b);
   return arr.length % 2 !== 0 ? nums[mid] : (nums[mid - 1] + nums[mid]) / 2;
 };
 
median([5, 6, 50, 1, -5]); // 5
-
beginner
minBy
Returns the minimum value of an array, after mapping each element to a value using the provided function.
Use Array.map() to map each element to the value returned by fn, Math.min() to get the maximum value.
const minBy = (arr, fn) => Math.min(...arr.map(typeof fn === 'function' ? fn : val => val[fn]));
+
minBy
Returns the minimum value of an array, after mapping each element to a value using the provided function.
Use Array.map() to map each element to the value returned by fn, Math.min() to get the maximum value.
const minBy = (arr, fn) => Math.min(...arr.map(typeof fn === 'function' ? fn : val => val[fn]));
 
minBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 2
 minBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 2
-
intermediate
percentile
Uses the percentile formula to calculate how many numbers in the given array are less or equal to the given value.
Use Array.reduce() to calculate how many numbers are below the value and how many are the same value and apply the percentile formula.
const percentile = (arr, val) =>
+
percentile
Uses the percentile formula to calculate how many numbers in the given array are less or equal to the given value.
Use Array.reduce() to calculate how many numbers are below the value and how many are the same value and apply the percentile formula.
const percentile = (arr, val) =>
   (100 * arr.reduce((acc, v) => acc + (v < val ? 1 : 0) + (v === val ? 0.5 : 0), 0)) / arr.length;
 
percentile([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 6); // 55
-
beginner
powerset
Returns the powerset of a given array of numbers.
Use Array.reduce() combined with Array.map() to iterate over elements and combine into an array containing all combinations.
const powerset = arr => arr.reduce((a, v) => a.concat(a.map(r => [v].concat(r))), [[]]);
+
powerset
Returns the powerset of a given array of numbers.
Use Array.reduce() combined with Array.map() to iterate over elements and combine into an array containing all combinations.
const powerset = arr => arr.reduce((a, v) => a.concat(a.map(r => [v].concat(r))), [[]]);
 
powerset([1, 2]); // [[], [1], [2], [2,1]]
-
intermediate
primes
Generates primes up to a given number, using the Sieve of Eratosthenes.
Generate an array from 2 to the given number. Use Array.filter() to filter out the values divisible by any number from 2 to the square root of the provided number.
const primes = num => {
+
primes
Generates primes up to a given number, using the Sieve of Eratosthenes.
Generate an array from 2 to the given number. Use Array.filter() to filter out the values divisible by any number from 2 to the square root of the provided number.
const primes = num => {
   let arr = Array.from({ length: num - 1 }).map((x, i) => i + 2),
     sqroot = Math.floor(Math.sqrt(num)),
     numsTillSqroot = Array.from({ length: sqroot - 1 }).map((x, i) => i + 2);
@@ -223,18 +223,18 @@ own individual rating by supplying it as the third argument.
   return arr;
 };
 
primes(10); // [2,3,5,7]
-
beginner
radsToDegrees
Converts an angle from radians to degrees.
Use Math.PI and the radian to degree formula to convert the angle from radians to degrees.
const radsToDegrees = rad => (rad * 180.0) / Math.PI;
+
radsToDegrees
Converts an angle from radians to degrees.
Use Math.PI and the radian to degree formula to convert the angle from radians to degrees.
const radsToDegrees = rad => (rad * 180.0) / Math.PI;
 
radsToDegrees(Math.PI / 2); // 90
-
intermediate
randomIntArrayInRange
Returns an array of n random integers in the specified range.
Use Array.from() to create an empty array of the specific length, Math.random() to generate a random number and map it to the desired range, using Math.floor() to make it an integer.
const randomIntArrayInRange = (min, max, n = 1) =>
+
randomIntArrayInRange
Returns an array of n random integers in the specified range.
Use Array.from() to create an empty array of the specific length, Math.random() to generate a random number and map it to the desired range, using Math.floor() to make it an integer.
const randomIntArrayInRange = (min, max, n = 1) =>
   Array.from({ length: n }, () => Math.floor(Math.random() * (max - min + 1)) + min);
 
randomIntArrayInRange(12, 35, 10); // [ 34, 14, 27, 17, 30, 27, 20, 26, 21, 14 ]
-
beginner
randomIntegerInRange
Returns a random integer in the specified range.
Use Math.random() to generate a random number and map it to the desired range, using Math.floor() to make it an integer.
const randomIntegerInRange = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
+
randomIntegerInRange
Returns a random integer in the specified range.
Use Math.random() to generate a random number and map it to the desired range, using Math.floor() to make it an integer.
const randomIntegerInRange = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
 
randomIntegerInRange(0, 5); // 2
-
beginner
randomNumberInRange
Returns a random number in the specified range.
Use Math.random() to generate a random value, map it to the desired range using multiplication.
const randomNumberInRange = (min, max) => Math.random() * (max - min) + min;
+
randomNumberInRange
Returns a random number in the specified range.
Use Math.random() to generate a random value, map it to the desired range using multiplication.
const randomNumberInRange = (min, max) => Math.random() * (max - min) + min;
 
randomNumberInRange(2, 10); // 6.0211363285087005
-
intermediate
round
Rounds a number to a specified amount of digits.
Use Math.round() and template literals to round the number to the specified number of digits. Omit the second argument, decimals to round to an integer.
const round = (n, decimals = 0) => Number(`${Math.round(`${n}e${decimals}`)}e-${decimals}`);
+
round
Rounds a number to a specified amount of digits.
Use Math.round() and template literals to round the number to the specified number of digits. Omit the second argument, decimals to round to an integer.
const round = (n, decimals = 0) => Number(`${Math.round(`${n}e${decimals}`)}e-${decimals}`);
 
round(1.005, 2); // 1.01
-
intermediate
sdbm
Hashes the input string into a whole number.
Use String.split('') and Array.reduce() to create a hash of the input string, utilizing bit shifting.
const sdbm = str => {
+
sdbm
Hashes the input string into a whole number.
Use String.split('') and Array.reduce() to create a hash of the input string, utilizing bit shifting.
const sdbm = str => {
   let arr = str.split('');
   return arr.reduce(
     (hashCode, currentVal) =>
@@ -243,7 +243,7 @@ own individual rating by supplying it as the third argument.
   );
 };
 
sdbm('name'); // -3521204949
-
intermediate
standardDeviation
Returns the standard deviation of an array of numbers.
Use Array.reduce() to calculate the mean, variance and the sum of the variance of the values, the variance of the values, then determine the standard deviation. You can omit the second argument to get the sample standard deviation or set it to true to get the population standard deviation.
const standardDeviation = (arr, usePopulation = false) => {
+
standardDeviation
Returns the standard deviation of an array of numbers.
Use Array.reduce() to calculate the mean, variance and the sum of the variance of the values, the variance of the values, then determine the standard deviation. You can omit the second argument to get the sample standard deviation or set it to true to get the population standard deviation.
const standardDeviation = (arr, usePopulation = false) => {
   const mean = arr.reduce((acc, val) => acc + val, 0) / arr.length;
   return Math.sqrt(
     arr.reduce((acc, val) => acc.concat((val - mean) ** 2), []).reduce((acc, val) => acc + val, 0) /
@@ -252,13 +252,13 @@ own individual rating by supplying it as the third argument.
 };
 
standardDeviation([10, 2, 38, 23, 38, 23, 21]); // 13.284434142114991 (sample)
 standardDeviation([10, 2, 38, 23, 38, 23, 21], true); // 12.29899614287479 (population)
-
beginner
sum
Returns the sum of two or more numbers/arrays.
Use Array.reduce() to add each value to an accumulator, initialized with a value of 0.
const sum = (...arr) => [...arr].reduce((acc, val) => acc + val, 0);
+
sum
Returns the sum of two or more numbers/arrays.
Use Array.reduce() to add each value to an accumulator, initialized with a value of 0.
const sum = (...arr) => [...arr].reduce((acc, val) => acc + val, 0);
 
sum(...[1, 2, 3, 4]); // 10
-
intermediate
sumBy
Returns the sum of an array, after mapping each element to a value using the provided function.
Use Array.map() to map each element to the value returned by fn, Array.reduce() to add each value to an accumulator, initialized with a value of 0.
const sumBy = (arr, fn) =>
+
sumBy
Returns the sum of an array, after mapping each element to a value using the provided function.
Use Array.map() to map each element to the value returned by fn, Array.reduce() to add each value to an accumulator, initialized with a value of 0.
const sumBy = (arr, fn) =>
   arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => acc + val, 0);
 
sumBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 20
 sumBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 20
-
intermediate
sumPower
Returns the sum of the powers of all the numbers from start to end (both inclusive).
Use Array.fill() to create an array of all the numbers in the target range, Array.map() and the exponent operator (**) to raise them to power and Array.reduce() to add them together. Omit the second argument, power, to use a default power of 2. Omit the third argument, start, to use a default starting value of 1.
const sumPower = (end, power = 2, start = 1) =>
+
sumPower
Returns the sum of the powers of all the numbers from start to end (both inclusive).
Use Array.fill() to create an array of all the numbers in the target range, Array.map() and the exponent operator (**) to raise them to power and Array.reduce() to add them together. Omit the second argument, power, to use a default power of 2. Omit the third argument, start, to use a default starting value of 1.
const sumPower = (end, power = 2, start = 1) =>
   Array(end + 1 - start)
     .fill(0)
     .map((x, i) => (i + start) ** power)
@@ -266,8 +266,8 @@ own individual rating by supplying it as the third argument.
 
sumPower(10); // 385
 sumPower(10, 3); //3025
 sumPower(10, 3, 5); //2925
-
beginner
toSafeInteger
Converts a value to a safe integer.
Use Math.max() and Math.min() to find the closest safe value. Use Math.round() to convert to an integer.
const toSafeInteger = num =>
+
toSafeInteger
Converts a value to a safe integer.
Use Math.max() and Math.min() to find the closest safe value. Use Math.round() to convert to an integer.
const toSafeInteger = num =>
   Math.round(Math.max(Math.min(num, Number.MAX_SAFE_INTEGER), Number.MIN_SAFE_INTEGER));
 
toSafeInteger('3.2'); // 3
 toSafeInteger(Infinity); // 9007199254740991
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/node.html b/docs/node.html index 8822f54b6..8c7f7dcee 100644 --- a/docs/node.html +++ b/docs/node.html @@ -73,11 +73,11 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Node

beginner

atob

Decodes a string of data which has been encoded using base-64 encoding.

Create a Buffer for the given string with base-64 encoding and use Buffer.toString('binary') to return the decoded string.

const atob = str => new Buffer(str, 'base64').toString('binary');
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Node
atob
Decodes a string of data which has been encoded using base-64 encoding.
Create a Buffer for the given string with base-64 encoding and use Buffer.toString('binary') to return the decoded string.
const atob = str => new Buffer(str, 'base64').toString('binary');
 
atob('Zm9vYmFy'); // 'foobar'
-
beginner
btoa
Creates a base-64 encoded ASCII string from a String object in which each character in the string is treated as a byte of binary data.
Create a Buffer for the given string with binary encoding and use Buffer.toString('base64') to return the encoded string.
const btoa = str => new Buffer(str, 'binary').toString('base64');
+
btoa
Creates a base-64 encoded ASCII string from a String object in which each character in the string is treated as a byte of binary data.
Create a Buffer for the given string with binary encoding and use Buffer.toString('base64') to return the encoded string.
const btoa = str => new Buffer(str, 'binary').toString('base64');
 
btoa('foobar'); // 'Zm9vYmFy'
-
intermediate
colorize
Add special characters to text to print in color in the console (combined with console.log()).
Use template literals and special characters to add the appropriate color code to the string output. For background colors, add a special character that resets the background color at the end of the string.
const colorize = (...args) => ({
+
colorize
Add special characters to text to print in color in the console (combined with console.log()).
Use template literals and special characters to add the appropriate color code to the string output. For background colors, add a special character that resets the background color at the end of the string.
const colorize = (...args) => ({
   black: `\x1b[30m${args.join(' ')}`,
   red: `\x1b[31m${args.join(' ')}`,
   green: `\x1b[32m${args.join(' ')}`,
@@ -98,13 +98,13 @@
 
console.log(colorize('foo').red); // 'foo' (red letters)
 console.log(colorize('foo', 'bar').bgBlue); // 'foo bar' (blue background)
 console.log(colorize(colorize('foo').yellow, colorize('foo').green).bgWhite); // 'foo bar' (first word in yellow letters, second word in green letters, white background for both)
-
intermediate
hasFlags
Check if the current process's arguments contain the specified flags.
Use Array.every() and Array.includes() to check if process.argv contains all the specified flags. Use a regular expression to test if the specified flags are prefixed with - or -- and prefix them accordingly.
const hasFlags = (...flags) =>
+
hasFlags
Check if the current process's arguments contain the specified flags.
Use Array.every() and Array.includes() to check if process.argv contains all the specified flags. Use a regular expression to test if the specified flags are prefixed with - or -- and prefix them accordingly.
const hasFlags = (...flags) =>
   flags.every(flag => process.argv.includes(/^-{1,2}/.test(flag) ? flag : '--' + flag));
 
// node myScript.js -s --test --cool=true
 hasFlags('-s'); // true
 hasFlags('--test', 'cool=true', '-s'); // true
 hasFlags('special'); // false
-
intermediate
hashNode
Creates a hash for a value using the SHA-256 algorithm. Returns a promise.
Use crypto API to create a hash for the given value.
const crypto = require('crypto');
+
hashNode
Creates a hash for a value using the SHA-256 algorithm. Returns a promise.
Use crypto API to create a hash for the given value.
const crypto = require('crypto');
 const hashNode = val =>
   new Promise(resolve =>
     setTimeout(
@@ -119,13 +119,13 @@ console.log<
     )
   );
 
hashNode(JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })).then(console.log); // '04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393'
-
intermediate
isTravisCI
Checks if the current environment is Travis CI.
Checks if the current environment has the TRAVIS and CI environment variables (reference).
const isTravisCI = () => 'TRAVIS' in process.env && 'CI' in process.env;
+
isTravisCI
Checks if the current environment is Travis CI.
Checks if the current environment has the TRAVIS and CI environment variables (reference).
const isTravisCI = () => 'TRAVIS' in process.env && 'CI' in process.env;
 
isTravisCI(); // true (if code is running on Travis CI)
-
intermediate
JSONToFile
Writes a JSON object to a file.
Use fs.writeFile(), template literals and JSON.stringify() to write a json object to a .json file.
const fs = require('fs');
+
JSONToFile
Writes a JSON object to a file.
Use fs.writeFile(), template literals and JSON.stringify() to write a json object to a .json file.
const fs = require('fs');
 const JSONToFile = (obj, filename) =>
   fs.writeFile(`${filename}.json`, JSON.stringify(obj, null, 2));
 
JSONToFile({ test: 'is passed' }, 'testJsonFile'); // writes the object to 'testJsonFile.json'
-
beginner
readFileLines
Returns an array of lines from the specified file.
Use readFileSync function in fs node package to create a Buffer from a file. convert buffer to string using toString(encoding) function. creating an array from contents of file by spliting file content line by line (each \n).
const fs = require('fs');
+
readFileLines
Returns an array of lines from the specified file.
Use readFileSync function in fs node package to create a Buffer from a file. convert buffer to string using toString(encoding) function. creating an array from contents of file by spliting file content line by line (each \n).
const fs = require('fs');
 const readFileLines = filename =>
   fs
     .readFileSync(filename)
@@ -140,12 +140,12 @@ contents of test.txt :
 */
 let arr = readFileLines('test.txt');
 console.log(arr); // ['line1', 'line2', 'line3']
-
beginner
untildify
Converts a tilde path to an absolute path.
Use String.replace() with a regular expression and OS.homedir() to replace the ~ in the start of the path with the home directory.
const untildify = str => str.replace(/^~($|\/|\\)/, `${require('os').homedir()}$1`);
+
untildify
Converts a tilde path to an absolute path.
Use String.replace() with a regular expression and OS.homedir() to replace the ~ in the start of the path with the home directory.
const untildify = str => str.replace(/^~($|\/|\\)/, `${require('os').homedir()}$1`);
 
untildify('~/node'); // '/Users/aUser/node'
-
intermediate
UUIDGeneratorNode
Generates a UUID in Node.JS.
Use crypto API to generate a UUID, compliant with RFC4122 version 4.
const crypto = require('crypto');
+
UUIDGeneratorNode
Generates a UUID in Node.JS.
Use crypto API to generate a UUID, compliant with RFC4122 version 4.
const crypto = require('crypto');
 const UUIDGeneratorNode = () =>
   ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
     (c ^ (crypto.randomBytes(1)[0] & (15 >> (c / 4)))).toString(16)
   );
 
UUIDGeneratorNode(); // '79c7c136-60ee-40a2-beb2-856f1feabefc'
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/object.html b/docs/object.html index e0ca15295..f3d2097ba 100644 --- a/docs/object.html +++ b/docs/object.html @@ -73,7 +73,7 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Object

intermediate

bindAll

Binds methods of an object to the object itself, overwriting the existing method.

Use Array.forEach() to return a function that uses Function.apply() to apply the given context (obj) to fn for each function specified.

const bindAll = (obj, ...fns) =>
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Object
bindAll
Binds methods of an object to the object itself, overwriting the existing method.
Use Array.forEach() to return a function that uses Function.apply() to apply the given context (obj) to fn for each function specified.
const bindAll = (obj, ...fns) =>
   fns.forEach(
     fn => (
       (f = obj[fn]),
@@ -90,7 +90,7 @@
 };
 bindAll(view, 'click');
 jQuery(element).on('click', view.click); // Logs 'clicked docs' when clicked.
-
intermediate
deepClone
Creates a deep clone of an object.
Use recursion. Use Object.assign() and an empty object ({}) to create a shallow clone of the original. Use Object.keys() and Array.forEach() to determine which key-value pairs need to be deep cloned.
const deepClone = obj => {
+
deepClone
Creates a deep clone of an object.
Use recursion. Use Object.assign() and an empty object ({}) to create a shallow clone of the original. Use Object.keys() and Array.forEach() to determine which key-value pairs need to be deep cloned.
const deepClone = obj => {
   let clone = Object.assign({}, obj);
   Object.keys(clone).forEach(
     key => (clone[key] = typeof obj[key] === 'object' ? deepClone(obj[key]) : obj[key])
@@ -99,7 +99,7 @@
 };
 
const a = { foo: 'bar', obj: { a: 1, b: 2 } };
 const b = deepClone(a); // a !== b, a.obj !== b.obj
-
intermediate
deepFreeze
Deep freezes an object.
Calls Object.freeze(obj) recursively on all unfrozen properties of passed object that are instanceof object.
const deepFreeze = obj =>
+
deepFreeze
Deep freezes an object.
Calls Object.freeze(obj) recursively on all unfrozen properties of passed object that are instanceof object.
const deepFreeze = obj =>
   Object.keys(obj).forEach(
     prop =>
       !obj[prop] instanceof Object || Object.isFrozen(obj[prop]) ? null : deepFreeze(obj[prop])
@@ -110,9 +110,9 @@
 
 o[0] = 3; // not allowed
 o[1][0] = 4; // not allowed as well
-
intermediate
defaults
Assigns default values for all properties in an object that are undefined.
Use Object.assign() to create a new empty object and copy the original one to maintain key order, use Array.reverse() and the spread operator ... to combine the default values from left to right, finally use obj again to overwrite properties that originally had a value.
const defaults = (obj, ...defs) => Object.assign({}, obj, ...defs.reverse(), obj);
+
defaults
Assigns default values for all properties in an object that are undefined.
Use Object.assign() to create a new empty object and copy the original one to maintain key order, use Array.reverse() and the spread operator ... to combine the default values from left to right, finally use obj again to overwrite properties that originally had a value.
const defaults = (obj, ...defs) => Object.assign({}, obj, ...defs.reverse(), obj);
 
defaults({ a: 1 }, { b: 2 }, { b: 6 }, { a: 3 }); // { a: 1, b: 2 }
-
intermediate
dig
Returns the target value in a nested JSON object, based on the given key.
Use the in operator to check if target exists in obj. If found, return the value of obj[target], otherwise use Object.values(obj) and Array.reduce() to recursively call dig on each nested object until the first matching key/value pair is found.
const dig = (obj, target) =>
+
dig
Returns the target value in a nested JSON object, based on the given key.
Use the in operator to check if target exists in obj. If found, return the value of obj[target], otherwise use Object.values(obj) and Array.reduce() to recursively call dig on each nested object until the first matching key/value pair is found.
const dig = (obj, target) =>
   target in obj
     ? obj[target]
     : Object.values(obj).reduce((acc, val) => {
@@ -128,7 +128,7 @@ o[1
 dig(data, 'level3'); // 'some data'
 dig(data, 'level4'); // undefined
-
advanced
equals
Performs a deep comparison between two values to determine if they are equivalent.
Check if the two values are identical, if they are both Date objects with the same time, using Date.getTime() or if they are both non-object values with an equivalent value (strict comparison). Check if only one value is null or undefined or if their prototypes differ. If none of the above conditions are met, use Object.keys() to check if both values have the same number of keys, then use Array.every() to check if every key in the first value exists in the second one and if they are equivalent by calling this method recursively.
const equals = (a, b) => {
+
equals
Performs a deep comparison between two values to determine if they are equivalent.
Check if the two values are identical, if they are both Date objects with the same time, using Date.getTime() or if they are both non-object values with an equivalent value (strict comparison). Check if only one value is null or undefined or if their prototypes differ. If none of the above conditions are met, use Object.keys() to check if both values have the same number of keys, then use Array.every() to check if every key in the first value exists in the second one and if they are equivalent by calling this method recursively.
const equals = (a, b) => {
   if (a === b) return true;
   if (a instanceof Date && b instanceof Date) return a.getTime() === b.getTime();
   if (!a || !b || (typeof a !== 'object' && typeof b !== 'object')) return a === b;
@@ -139,7 +139,7 @@ o[1return keys.every(k => equals(a[k], b[k]));
 };
 
equals({ a: [2, { e: 3 }], b: [4], c: 'foo' }, { a: [2, { e: 3 }], b: [4], c: 'foo' }); // true
-
intermediate
findKey
Returns the first key that satisfies the provided testing function. Otherwise undefined is returned.
Use Object.keys(obj) to get all the properties of the object, Array.find() to test the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
const findKey = (obj, fn) => Object.keys(obj).find(key => fn(obj[key], key, obj));
+
findKey
Returns the first key that satisfies the provided testing function. Otherwise undefined is returned.
Use Object.keys(obj) to get all the properties of the object, Array.find() to test the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
const findKey = (obj, fn) => Object.keys(obj).find(key => fn(obj[key], key, obj));
 
findKey(
   {
     barney: { age: 36, active: true },
@@ -148,7 +148,7 @@ o[1
   o => o['active']
 ); // 'barney'
-
intermediate
findLastKey
Returns the last key that satisfies the provided testing function. Otherwise undefined is returned.
Use Object.keys(obj) to get all the properties of the object, Array.reverse() to reverse their order and Array.find() to test the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
const findLastKey = (obj, fn) =>
+
findLastKey
Returns the last key that satisfies the provided testing function. Otherwise undefined is returned.
Use Object.keys(obj) to get all the properties of the object, Array.reverse() to reverse their order and Array.find() to test the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
const findLastKey = (obj, fn) =>
   Object.keys(obj)
     .reverse()
     .find(key => fn(obj[key], key, obj));
@@ -160,7 +160,7 @@ o[1
   o => o['active']
 ); // 'pebbles'
-
intermediate
flattenObject
Flatten an object with the paths for keys.
Use recursion. Use Object.keys(obj) combined with Array.reduce() to convert every leaf node to a flattened path node. If the value of a key is an object, the function calls itself with the appropriate prefix to create the path using Object.assign(). Otherwise, it adds the appropriate prefixed key-value pair to the accumulator object. You should always omit the second argument, prefix, unless you want every key to have a prefix.
const flattenObject = (obj, prefix = '') =>
+
flattenObject
Flatten an object with the paths for keys.
Use recursion. Use Object.keys(obj) combined with Array.reduce() to convert every leaf node to a flattened path node. If the value of a key is an object, the function calls itself with the appropriate prefix to create the path using Object.assign(). Otherwise, it adds the appropriate prefixed key-value pair to the accumulator object. You should always omit the second argument, prefix, unless you want every key to have a prefix.
const flattenObject = (obj, prefix = '') =>
   Object.keys(obj).reduce((acc, k) => {
     const pre = prefix.length ? prefix + '.' : '';
     if (typeof obj[k] === 'object') Object.assign(acc, flattenObject(obj[k], pre + k));
@@ -168,14 +168,14 @@ o[1return acc;
   }, {});
 
flattenObject({ a: { b: { c: 1 } }, d: 1 }); // { 'a.b.c': 1, d: 1 }
-
intermediate
forOwn
Iterates over all own properties of an object, running a callback for each one.
Use Object.keys(obj) to get all the properties of the object, Array.forEach() to run the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
const forOwn = (obj, fn) => Object.keys(obj).forEach(key => fn(obj[key], key, obj));
+
forOwn
Iterates over all own properties of an object, running a callback for each one.
Use Object.keys(obj) to get all the properties of the object, Array.forEach() to run the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
const forOwn = (obj, fn) => Object.keys(obj).forEach(key => fn(obj[key], key, obj));
 
forOwn({ foo: 'bar', a: 1 }, v => console.log(v)); // 'bar', 1
-
intermediate
forOwnRight
Iterates over all own properties of an object in reverse, running a callback for each one.
Use Object.keys(obj) to get all the properties of the object, Array.reverse() to reverse their order and Array.forEach() to run the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
const forOwnRight = (obj, fn) =>
+
forOwnRight
Iterates over all own properties of an object in reverse, running a callback for each one.
Use Object.keys(obj) to get all the properties of the object, Array.reverse() to reverse their order and Array.forEach() to run the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
const forOwnRight = (obj, fn) =>
   Object.keys(obj)
     .reverse()
     .forEach(key => fn(obj[key], key, obj));
 
forOwnRight({ foo: 'bar', a: 1 }, v => console.log(v)); // 1, 'bar'
-
intermediate
functions
Returns an array of function property names from own (and optionally inherited) enumerable properties of an object.
Use Object.keys(obj) to iterate over the object's own properties. If inherited is true, use Object.get.PrototypeOf(obj) to also get the object's inherited properties. Use Array.filter() to keep only those properties that are functions. Omit the second argument, inherited, to not include inherited properties by default.
const functions = (obj, inherited = false) =>
+
functions
Returns an array of function property names from own (and optionally inherited) enumerable properties of an object.
Use Object.keys(obj) to iterate over the object's own properties. If inherited is true, use Object.get.PrototypeOf(obj) to also get the object's inherited properties. Use Array.filter() to keep only those properties that are functions. Omit the second argument, inherited, to not include inherited properties by default.
const functions = (obj, inherited = false) =>
   (inherited
     ? [...Object.keys(obj), ...Object.keys(Object.getPrototypeOf(obj))]
     : Object.keys(obj)
@@ -187,7 +187,7 @@ o[1.prototype.c = () => 3;
 functions(new Foo()); // ['a', 'b']
 functions(new Foo(), true); // ['a', 'b', 'c']
-
intermediate
get
Retrieve a set of properties indicated by the given selectors from an object.
Use Array.map() for each selector, String.replace() to replace square brackets with dots, String.split('.') to split each selector, Array.filter() to remove empty values and Array.reduce() to get the value indicated by it.
const get = (from, ...selectors) =>
+
get
Retrieve a set of properties indicated by the given selectors from an object.
Use Array.map() for each selector, String.replace() to replace square brackets with dots, String.split('.') to split each selector, Array.filter() to remove empty values and Array.reduce() to get the value indicated by it.
const get = (from, ...selectors) =>
   [...selectors].map(s =>
     s
       .replace(/\[([^\[\]]*)\]/g, '.$1.')
@@ -197,7 +197,7 @@ Foo.prototypeexamples
const obj = { selector: { to: { val: 'val to select' } }, target: [1, 2, { a: 'test' }] };
 get(obj, 'selector.to.val', 'target[0]', 'target[2].a'); // ['val to select', 1, 'test']
-
intermediate
invertKeyValues
Inverts the key-value pairs of an object, without mutating it. The corresponding inverted value of each inverted key is an array of keys responsible for generating the inverted value. If a function is supplied, it is applied to each inverted key.
Use Object.keys() and Array.reduce() to invert the key-value pairs of an object and apply the function provided (if any). Omit the second argument, fn, to get the inverted keys without applying a function to them.
const invertKeyValues = (obj, fn) =>
+
invertKeyValues
Inverts the key-value pairs of an object, without mutating it. The corresponding inverted value of each inverted key is an array of keys responsible for generating the inverted value. If a function is supplied, it is applied to each inverted key.
Use Object.keys() and Array.reduce() to invert the key-value pairs of an object and apply the function provided (if any). Omit the second argument, fn, to get the inverted keys without applying a function to them.
const invertKeyValues = (obj, fn) =>
   Object.keys(obj).reduce((acc, key) => {
     const val = fn ? fn(obj[key]) : obj[key];
     acc[val] = acc[val] || [];
@@ -206,20 +206,20 @@ Foo.prototypeexamples
invertKeyValues({ a: 1, b: 2, c: 1 }); // { 1: [ 'a', 'c' ], 2: [ 'b' ] }
 invertKeyValues({ a: 1, b: 2, c: 1 }, value => 'group' + value); // { group1: [ 'a', 'c' ], group2: [ 'b' ] }
-
intermediate
lowercaseKeys
Creates a new object from the specified object, where all the keys are in lowercase.
Use Object.keys() and Array.reduce() to create a new object from the specified object. Convert each key in the original object to lowercase, using String.toLowerCase().
const lowercaseKeys = obj =>
+
lowercaseKeys
Creates a new object from the specified object, where all the keys are in lowercase.
Use Object.keys() and Array.reduce() to create a new object from the specified object. Convert each key in the original object to lowercase, using String.toLowerCase().
const lowercaseKeys = obj =>
   Object.keys(obj).reduce((acc, key) => {
     acc[key.toLowerCase()] = obj[key];
     return acc;
   }, {});
 
const myObj = { Name: 'Adam', sUrnAME: 'Smith' };
 const myObjLower = lowercaseKeys(myObj); // {name: 'Adam', surname: 'Smith'};
-
intermediate
mapKeys
Creates an object with keys generated by running the provided function for each key and the same values as the provided object.
Use Object.keys(obj) to iterate over the object's keys. Use Array.reduce() to create a new object with the same values and mapped keys using fn.
const mapKeys = (obj, fn) =>
+
mapKeys
Creates an object with keys generated by running the provided function for each key and the same values as the provided object.
Use Object.keys(obj) to iterate over the object's keys. Use Array.reduce() to create a new object with the same values and mapped keys using fn.
const mapKeys = (obj, fn) =>
   Object.keys(obj).reduce((acc, k) => {
     acc[fn(obj[k], k, obj)] = obj[k];
     return acc;
   }, {});
 
mapKeys({ a: 1, b: 2 }, (val, key) => key + val); // { a1: 1, b2: 2 }
-
intermediate
mapValues
Creates an object with the same keys as the provided object and values generated by running the provided function for each value.
Use Object.keys(obj) to iterate over the object's keys. Use Array.reduce() to create a new object with the same keys and mapped values using fn.
const mapValues = (obj, fn) =>
+
mapValues
Creates an object with the same keys as the provided object and values generated by running the provided function for each value.
Use Object.keys(obj) to iterate over the object's keys. Use Array.reduce() to create a new object with the same keys and mapped values using fn.
const mapValues = (obj, fn) =>
   Object.keys(obj).reduce((acc, k) => {
     acc[k] = fn(obj[k], k, obj);
     return acc;
@@ -229,11 +229,11 @@ Foo.prototype: { user: 'pebbles', age: 1 }
 };
 mapValues(users, u => u.age); // { fred: 40, pebbles: 1 }
-
intermediate
matches
Compares two objects to determine if the first one contains equivalent property values to the second one.
Use Object.keys(source) to get all the keys of the second object, then Array.every(), Object.hasOwnProperty() and strict comparison to determine if all keys exist in the first object and have the same values.
const matches = (obj, source) =>
+
matches
Compares two objects to determine if the first one contains equivalent property values to the second one.
Use Object.keys(source) to get all the keys of the second object, then Array.every(), Object.hasOwnProperty() and strict comparison to determine if all keys exist in the first object and have the same values.
const matches = (obj, source) =>
   Object.keys(source).every(key => obj.hasOwnProperty(key) && obj[key] === source[key]);
 
matches({ age: 25, hair: 'long', beard: true }, { hair: 'long', beard: true }); // true
 matches({ hair: 'long', beard: true }, { age: 25, hair: 'long', beard: true }); // false
-
intermediate
matchesWith
Compares two objects to determine if the first one contains equivalent property values to the second one, based on a provided function.
Use Object.keys(source) to get all the keys of the second object, then Array.every(), Object.hasOwnProperty() and the provided function to determine if all keys exist in the first object and have equivalent values. If no function is provided, the values will be compared using the equality operator.
const matchesWith = (obj, source, fn) =>
+
matchesWith
Compares two objects to determine if the first one contains equivalent property values to the second one, based on a provided function.
Use Object.keys(source) to get all the keys of the second object, then Array.every(), Object.hasOwnProperty() and the provided function to determine if all keys exist in the first object and have equivalent values. If no function is provided, the values will be compared using the equality operator.
const matchesWith = (obj, source, fn) =>
   Object.keys(source).every(
     key =>
       obj.hasOwnProperty(key) && fn
@@ -246,7 +246,7 @@ Foo.prototype: 'hi' },
   (oV, sV) => isGreeting(oV) && isGreeting(sV)
 ); // true
-
intermediate
merge
Creates a new object from the combination of two or more objects.
Use Array.reduce() combined with Object.keys(obj) to iterate over all objects and keys. Use hasOwnProperty() and Array.concat() to append values for keys existing in multiple objects.
const merge = (...objs) =>
+
merge
Creates a new object from the combination of two or more objects.
Use Array.reduce() combined with Object.keys(obj) to iterate over all objects and keys. Use hasOwnProperty() and Array.concat() to append values for keys existing in multiple objects.
const merge = (...objs) =>
   [...objs].reduce(
     (acc, obj) =>
       Object.keys(obj).reduce((a, k) => {
@@ -265,7 +265,7 @@ Foo.prototype: 'foo'
 };
 merge(object, other); // { a: [ { x: 2 }, { y: 4 }, { z: 3 } ], b: [ 1, 2, 3 ], c: 'foo' }
-
intermediate
nest
Given a flat array of objects linked to one another, it will nest them recursively. Useful for nesting comments, such as the ones on reddit.com.
Use recursion. Use Array.filter() to filter the items where the id matches the link, then Array.map() to map each one to a new object that has a children property which recursively nests the items based on which ones are children of the current item. Omit the second argument, id, to default to null which indicates the object is not linked to another one (i.e. it is a top level object). Omit the third argument, link, to use 'parent_id' as the default property which links the object to another one by its id.
const nest = (items, id = null, link = 'parent_id') =>
+
nest
Given a flat array of objects linked to one another, it will nest them recursively. Useful for nesting comments, such as the ones on reddit.com.
Use recursion. Use Array.filter() to filter the items where the id matches the link, then Array.map() to map each one to a new object that has a children property which recursively nests the items based on which ones are children of the current item. Omit the second argument, id, to default to null which indicates the object is not linked to another one (i.e. it is a top level object). Omit the third argument, link, to use 'parent_id' as the default property which links the object to another one by its id.
const nest = (items, id = null, link = 'parent_id') =>
   items
     .filter(item => item[link] === id)
     .map(item => ({ ...item, children: nest(items, item.id) }));
@@ -278,21 +278,21 @@ Foo.prototype: 5, parent_id: 4 }
 ];
 const nestedComments = nest(comments); // [{ id: 1, parent_id: null, children: [...] }]
-
beginner
objectFromPairs
Creates an object from the given key-value pairs.
Use Array.reduce() to create and combine key-value pairs.
const objectFromPairs = arr => arr.reduce((a, v) => ((a[v[0]] = v[1]), a), {});
+
objectFromPairs
Creates an object from the given key-value pairs.
Use Array.reduce() to create and combine key-value pairs.
const objectFromPairs = arr => arr.reduce((a, v) => ((a[v[0]] = v[1]), a), {});
 
objectFromPairs([['a', 1], ['b', 2]]); // {a: 1, b: 2}
-
beginner
objectToPairs
Creates an array of key-value pair arrays from an object.
Use Object.keys() and Array.map() to iterate over the object's keys and produce an array with key-value pairs.
const objectToPairs = obj => Object.keys(obj).map(k => [k, obj[k]]);
+
objectToPairs
Creates an array of key-value pair arrays from an object.
Use Object.keys() and Array.map() to iterate over the object's keys and produce an array with key-value pairs.
const objectToPairs = obj => Object.keys(obj).map(k => [k, obj[k]]);
 
objectToPairs({ a: 1, b: 2 }); // [['a',1],['b',2]]
-
intermediate
omit
Omits the key-value pairs corresponding to the given keys from an object.
Use Object.keys(obj), Array.filter() and Array.includes() to remove the provided keys. Use Array.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
const omit = (obj, arr) =>
+
omit
Omits the key-value pairs corresponding to the given keys from an object.
Use Object.keys(obj), Array.filter() and Array.includes() to remove the provided keys. Use Array.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
const omit = (obj, arr) =>
   Object.keys(obj)
     .filter(k => !arr.includes(k))
     .reduce((acc, key) => ((acc[key] = obj[key]), acc), {});
 
omit({ a: 1, b: '2', c: 3 }, ['b']); // { 'a': 1, 'c': 3 }
-
intermediate
omitBy
Creates an object composed of the properties the given function returns falsey for. The function is invoked with two arguments: (value, key).
Use Object.keys(obj) and Array.filter()to remove the keys for which fn returns a truthy value. Use Array.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
const omitBy = (obj, fn) =>
+
omitBy
Creates an object composed of the properties the given function returns falsey for. The function is invoked with two arguments: (value, key).
Use Object.keys(obj) and Array.filter()to remove the keys for which fn returns a truthy value. Use Array.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
const omitBy = (obj, fn) =>
   Object.keys(obj)
     .filter(k => !fn(obj[k], k))
     .reduce((acc, key) => ((acc[key] = obj[key]), acc), {});
 
omitBy({ a: 1, b: '2', c: 3 }, x => typeof x === 'number'); // { b: '2' }
-
intermediate
orderBy
Returns a sorted array of objects ordered by properties and orders.
Uses Array.sort(), Array.reduce() on the props array with a default value of 0, use array destructuring to swap the properties position depending on the order passed. If no orders array is passed it sort by 'asc' by default.
const orderBy = (arr, props, orders) =>
+
orderBy
Returns a sorted array of objects ordered by properties and orders.
Uses Array.sort(), Array.reduce() on the props array with a default value of 0, use array destructuring to swap the properties position depending on the order passed. If no orders array is passed it sort by 'asc' by default.
const orderBy = (arr, props, orders) =>
   [...arr].sort((a, b) =>
     props.reduce((acc, prop, i) => {
       if (acc === 0) {
@@ -305,15 +305,15 @@ Foo.prototypeexamples
const users = [{ name: 'fred', age: 48 }, { name: 'barney', age: 36 }, { name: 'fred', age: 40 }];
 orderBy(users, ['name', 'age'], ['asc', 'desc']); // [{name: 'barney', age: 36}, {name: 'fred', age: 48}, {name: 'fred', age: 40}]
 orderBy(users, ['name', 'age']); // [{name: 'barney', age: 36}, {name: 'fred', age: 40}, {name: 'fred', age: 48}]
-
intermediate
pick
Picks the key-value pairs corresponding to the given keys from an object.
Use Array.reduce() to convert the filtered/picked keys back to an object with the corresponding key-value pairs if the key exists in the object.
const pick = (obj, arr) =>
+
pick
Picks the key-value pairs corresponding to the given keys from an object.
Use Array.reduce() to convert the filtered/picked keys back to an object with the corresponding key-value pairs if the key exists in the object.
const pick = (obj, arr) =>
   arr.reduce((acc, curr) => (curr in obj && (acc[curr] = obj[curr]), acc), {});
 
pick({ a: 1, b: '2', c: 3 }, ['a', 'c']); // { 'a': 1, 'c': 3 }
-
intermediate
pickBy
Creates an object composed of the properties the given function returns truthy for. The function is invoked with two arguments: (value, key).
Use Object.keys(obj) and Array.filter()to remove the keys for which fn returns a falsey value. Use Array.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
const pickBy = (obj, fn) =>
+
pickBy
Creates an object composed of the properties the given function returns truthy for. The function is invoked with two arguments: (value, key).
Use Object.keys(obj) and Array.filter()to remove the keys for which fn returns a falsey value. Use Array.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
const pickBy = (obj, fn) =>
   Object.keys(obj)
     .filter(k => fn(obj[k], k))
     .reduce((acc, key) => ((acc[key] = obj[key]), acc), {});
 
pickBy({ a: 1, b: '2', c: 3 }, x => typeof x === 'number'); // { 'a': 1, 'c': 3 }
-
intermediate
renameKeys
Replaces the names of multiple object keys with the values provided.
Use Object.keys() in combination with Array.reduce() and the spread operator (...) to get the object's keys and rename them according to keysMap.
const renameKeys = (keysMap, obj) =>
+
renameKeys
Replaces the names of multiple object keys with the values provided.
Use Object.keys() in combination with Array.reduce() and the spread operator (...) to get the object's keys and rename them according to keysMap.
const renameKeys = (keysMap, obj) =>
   Object.keys(obj).reduce(
     (acc, key) => ({
       ...acc,
@@ -323,10 +323,10 @@ Foo.prototypeexamples
const obj = { name: 'Bobo', job: 'Front-End Master', shoeSize: 100 };
 renameKeys({ name: 'firstName', job: 'passion' }, obj); // { firstName: 'Bobo', passion: 'Front-End Master', shoeSize: 100 }
-
beginner
shallowClone
Creates a shallow clone of an object.
Use Object.assign() and an empty object ({}) to create a shallow clone of the original.
const shallowClone = obj => Object.assign({}, obj);
+
shallowClone
Creates a shallow clone of an object.
Use Object.assign() and an empty object ({}) to create a shallow clone of the original.
const shallowClone = obj => Object.assign({}, obj);
 
const a = { x: true, y: 1 };
 const b = shallowClone(a); // a !== b
-
intermediate
size
Get size of arrays, objects or strings.
Get type of val (array, object or string). Use length property for arrays. Use length or size value if available or number of keys for objects. Use size of a Blob object created from val for strings.
Split strings into array of characters with split('') and return its length.
const size = val =>
+
size
Get size of arrays, objects or strings.
Get type of val (array, object or string). Use length property for arrays. Use length or size value if available or number of keys for objects. Use size of a Blob object created from val for strings.
Split strings into array of characters with split('') and return its length.
const size = val =>
   Array.isArray(val)
     ? val.length
     : val && typeof val === 'object'
@@ -337,7 +337,7 @@ Foo.prototypeexamples
size([1, 2, 3, 4, 5]); // 5
 size('size'); // 4
 size({ one: 1, two: 2, three: 3 }); // 3
-
intermediate
transform
Applies a function against an accumulator and each key in the object (from left to right).
Use Object.keys(obj) to iterate over each key in the object, Array.reduce() to call the apply the specified function against the given accumulator.
const transform = (obj, fn, acc) => Object.keys(obj).reduce((a, k) => fn(a, obj[k], k, obj), acc);
+
transform
Applies a function against an accumulator and each key in the object (from left to right).
Use Object.keys(obj) to iterate over each key in the object, Array.reduce() to call the apply the specified function against the given accumulator.
const transform = (obj, fn, acc) => Object.keys(obj).reduce((a, k) => fn(a, obj[k], k, obj), acc);
 
transform(
   { a: 1, b: 2, c: 1 },
   (r, v, k) => {
@@ -346,9 +346,9 @@ Foo.prototype// { '1': ['a', 'c'], '2': ['b'] }
-
intermediate
truthCheckCollection
Checks if the predicate (second argument) is truthy on all elements of a collection (first argument).
Use Array.every() to check if each passed object has the specified property and if it returns a truthy value.
const truthCheckCollection = (collection, pre) => collection.every(obj => obj[pre]);
+
truthCheckCollection
Checks if the predicate (second argument) is truthy on all elements of a collection (first argument).
Use Array.every() to check if each passed object has the specified property and if it returns a truthy value.
const truthCheckCollection = (collection, pre) => collection.every(obj => obj[pre]);
 
truthCheckCollection([{ user: 'Tinky-Winky', sex: 'male' }, { user: 'Dipsy', sex: 'male' }], 'sex'); // true
-
advanced
unflattenObject
Unflatten an object with the paths for keys.
Use Object.keys(obj) combined with Array.reduce() to convert flattened path node to a leaf node. If the value of a key contains a dot delimiter (.), use Array.split('.'), string transformations and JSON.parse() to create an object, then Object.assign() to create the leaf node. Otherwise, add the appropriate key-value pair to the accumulator object.
const unflattenObject = obj =>
+
unflattenObject
Unflatten an object with the paths for keys.
Use Object.keys(obj) combined with Array.reduce() to convert flattened path node to a leaf node. If the value of a key contains a dot delimiter (.), use Array.split('.'), string transformations and JSON.parse() to create an object, then Object.assign() to create the leaf node. Otherwise, add the appropriate key-value pair to the accumulator object.
const unflattenObject = obj =>
   Object.keys(obj).reduce((acc, k) => {
     if (k.indexOf('.') !== -1) {
       const keys = k.split('.');
@@ -365,4 +365,4 @@ Foo.prototypereturn acc;
   }, {});
 
unflattenObject({ 'a.b.c': 1, d: 1 }); // { a: { b: { c: 1 } }, d: 1 }
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/scss/style.scss b/docs/scss/style.scss index 70d0d185c..4db083131 100644 --- a/docs/scss/style.scss +++ b/docs/scss/style.scss @@ -614,8 +614,8 @@ h2.category-name { position: absolute; top: -0.5rem; right: -2.125rem; - width: 6.5rem; - height: 3.25rem; + width: 4rem; + height: 2rem; padding-top: 2rem; transform: rotate(45deg); text-align: center; diff --git a/docs/string.html b/docs/string.html index 358c4affa..f69f3a8c7 100644 --- a/docs/string.html +++ b/docs/string.html @@ -73,16 +73,16 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



String

beginner

byteSize

Returns the length of a string in bytes.

Convert a given string to a Blob Object and find its size.

const byteSize = str => new Blob([str]).size;
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


String
byteSize
Returns the length of a string in bytes.
Convert a given string to a Blob Object and find its size.
const byteSize = str => new Blob([str]).size;
 
byteSize('😀'); // 4
 byteSize('Hello World'); // 11
-
intermediate
capitalize
Capitalizes the first letter of a string.
Use array destructuring and String.toUpperCase() to capitalize first letter, ...rest to get array of characters after first letter and then Array.join('') to make it a string again. Omit the lowerRest parameter to keep the rest of the string intact, or set it to true to convert to lowercase.
const capitalize = ([first, ...rest], lowerRest = false) =>
+
capitalize
Capitalizes the first letter of a string.
Use array destructuring and String.toUpperCase() to capitalize first letter, ...rest to get array of characters after first letter and then Array.join('') to make it a string again. Omit the lowerRest parameter to keep the rest of the string intact, or set it to true to convert to lowercase.
const capitalize = ([first, ...rest], lowerRest = false) =>
   first.toUpperCase() + (lowerRest ? rest.join('').toLowerCase() : rest.join(''));
 
capitalize('fooBar'); // 'FooBar'
 capitalize('fooBar', true); // 'Foobar'
-
intermediate
capitalizeEveryWord
Capitalizes the first letter of every word in a string.
Use String.replace() to match the first character of each word and String.toUpperCase() to capitalize it.
const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());
+
capitalizeEveryWord
Capitalizes the first letter of every word in a string.
Use String.replace() to match the first character of each word and String.toUpperCase() to capitalize it.
const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());
 
capitalizeEveryWord('hello world!'); // 'Hello World!'
-
intermediate
CSVToArray
Converts a comma-separated values (CSV) string to a 2D array.
Use Array.slice() and Array.indexOf('\n') to remove the first row (title row) if omitFirstRow is true. Use String.split('\n') to create a string for each row, then String.split(delimiter) to separate the values in each row. Omit the second argument, delimiter, to use a default delimiter of ,. Omit the third argument, omitFirstRow, to include the first row (title row) of the CSV string.
const CSVToArray = (data, delimiter = ',', omitFirstRow = false) =>
+
CSVToArray
Converts a comma-separated values (CSV) string to a 2D array.
Use Array.slice() and Array.indexOf('\n') to remove the first row (title row) if omitFirstRow is true. Use String.split('\n') to create a string for each row, then String.split(delimiter) to separate the values in each row. Omit the second argument, delimiter, to use a default delimiter of ,. Omit the third argument, omitFirstRow, to include the first row (title row) of the CSV string.
const CSVToArray = (data, delimiter = ',', omitFirstRow = false) =>
   data
     .slice(omitFirstRow ? data.indexOf('\n') + 1 : 0)
     .split('\n')
@@ -90,7 +90,7 @@
 
CSVToArray('a,b\nc,d'); // [['a','b'],['c','d']];
 CSVToArray('a;b\nc;d', ';'); // [['a','b'],['c','d']];
 CSVToArray('col1,col2\na,b\nc,d', ',', true); // [['a','b'],['c','d']];
-
advanced
CSVToJSON
Converts a comma-separated values (CSV) string to a 2D array of objects. The first row of the string is used as the title row.
Use Array.slice() and Array.indexOf('\n') and String.split(delimiter) to separate the first row (title row) into values. Use String.split('\n') to create a string for each row, then Array.map() and String.split(delimiter) to separate the values in each row. Use Array.reduce() to create an object for each row's values, with the keys parsed from the title row. Omit the second argument, delimiter, to use a default delimiter of ,.
const CSVToJSON = (data, delimiter = ',') => {
+
CSVToJSON
Converts a comma-separated values (CSV) string to a 2D array of objects. The first row of the string is used as the title row.
Use Array.slice() and Array.indexOf('\n') and String.split(delimiter) to separate the first row (title row) into values. Use String.split('\n') to create a string for each row, then Array.map() and String.split(delimiter) to separate the values in each row. Use Array.reduce() to create an object for each row's values, with the keys parsed from the title row. Omit the second argument, delimiter, to use a default delimiter of ,.
const CSVToJSON = (data, delimiter = ',') => {
   const titles = data.slice(0, data.indexOf('\n')).split(delimiter);
   return data
     .slice(data.indexOf('\n') + 1)
@@ -102,11 +102,11 @@
 };
 
CSVToJSON('col1,col2\na,b\nc,d'); // [{'col1': 'a', 'col2': 'b'}, {'col1': 'c', 'col2': 'd'}];
 CSVToJSON('col1;col2\na;b\nc;d', ';'); // [{'col1': 'a', 'col2': 'b'}, {'col1': 'c', 'col2': 'd'}];
-
intermediate
decapitalize
Decapitalizes the first letter of a string.
Use array destructuring and String.toLowerCase() to decapitalize first letter, ...rest to get array of characters after first letter and then Array.join('') to make it a string again. Omit the upperRest parameter to keep the rest of the string intact, or set it to true to convert to uppercase.
const decapitalize = ([first, ...rest], upperRest = false) =>
+
decapitalize
Decapitalizes the first letter of a string.
Use array destructuring and String.toLowerCase() to decapitalize first letter, ...rest to get array of characters after first letter and then Array.join('') to make it a string again. Omit the upperRest parameter to keep the rest of the string intact, or set it to true to convert to uppercase.
const decapitalize = ([first, ...rest], upperRest = false) =>
   first.toLowerCase() + (upperRest ? rest.join('').toUpperCase() : rest.join(''));
 
decapitalize('FooBar'); // 'fooBar'
 decapitalize('FooBar', true); // 'fOOBAR'
-
intermediate
escapeHTML
Escapes a string for use in HTML.
Use String.replace() with a regexp that matches the characters that need to be escaped, using a callback function to replace each character instance with its associated escaped character using a dictionary (object).
const escapeHTML = str =>
+
escapeHTML
Escapes a string for use in HTML.
Use String.replace() with a regexp that matches the characters that need to be escaped, using a callback function to replace each character instance with its associated escaped character using a dictionary (object).
const escapeHTML = str =>
   str.replace(
     /[&<>'"]/g,
     tag =>
@@ -119,9 +119,9 @@
       }[tag] || tag)
   );
 
escapeHTML('<a href="#">Me & you</a>'); // '&lt;a href=&quot;#&quot;&gt;Me &amp; you&lt;/a&gt;'
-
intermediate
escapeRegExp
Escapes a string to use in a regular expression.
Use String.replace() to escape special characters.
const escapeRegExp = str => str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+
escapeRegExp
Escapes a string to use in a regular expression.
Use String.replace() to escape special characters.
const escapeRegExp = str => str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
 
escapeRegExp('(test)'); // \\(test\\)
-
intermediate
fromCamelCase
Converts a string from camelcase.
Use String.replace() to remove underscores, hyphens, and spaces and convert words to camelcase. Omit the second argument to use a default separator of _.
const fromCamelCase = (str, separator = '_') =>
+
fromCamelCase
Converts a string from camelcase.
Use String.replace() to remove underscores, hyphens, and spaces and convert words to camelcase. Omit the second argument to use a default separator of _.
const fromCamelCase = (str, separator = '_') =>
   str
     .replace(/([a-z\d])([A-Z])/g, '$1' + separator + '$2')
     .replace(/([A-Z]+)([A-Z][a-z\d]+)/g, '$1' + separator + '$2')
@@ -129,11 +129,11 @@
 
fromCamelCase('someDatabaseFieldName', ' '); // 'some database field name'
 fromCamelCase('someLabelThatNeedsToBeCamelized', '-'); // 'some-label-that-needs-to-be-camelized'
 fromCamelCase('someJavascriptProperty', '_'); // 'some_javascript_property'
-
intermediate
isAbsoluteURL
Returns true if the given string is an absolute URL, false otherwise.
Use a regular expression to test if the string is an absolute URL.
const isAbsoluteURL = str => /^[a-z][a-z0-9+.-]*:/.test(str);
+
isAbsoluteURL
Returns true if the given string is an absolute URL, false otherwise.
Use a regular expression to test if the string is an absolute URL.
const isAbsoluteURL = str => /^[a-z][a-z0-9+.-]*:/.test(str);
 
isAbsoluteURL('https://google.com'); // true
 isAbsoluteURL('ftp://www.myserver.net'); // true
 isAbsoluteURL('/foo/bar'); // false
-
intermediate
isAnagram
Checks if a string is an anagram of another string (case-insensitive, ignores spaces, punctuation and special characters).
Use String.toLowerCase(), String.replace() with an appropriate regular expression to remove unnecessary characters, String.split(''), Array.sort() and Array.join('') on both strings to normalize them, then check if their normalized forms are equal.
const isAnagram = (str1, str2) => {
+
isAnagram
Checks if a string is an anagram of another string (case-insensitive, ignores spaces, punctuation and special characters).
Use String.toLowerCase(), String.replace() with an appropriate regular expression to remove unnecessary characters, String.split(''), Array.sort() and Array.join('') on both strings to normalize them, then check if their normalized forms are equal.
const isAnagram = (str1, str2) => {
   const normalize = str =>
     str
       .toLowerCase()
@@ -144,36 +144,36 @@
   return normalize(str1) === normalize(str2);
 };
 
isAnagram('iceman', 'cinema'); // true
-
beginner
isLowerCase
Checks if a string is lower case.
Convert the given string to lower case, using String.toLowerCase() and compare it to the original.
const isLowerCase = str => str === str.toLowerCase();
+
isLowerCase
Checks if a string is lower case.
Convert the given string to lower case, using String.toLowerCase() and compare it to the original.
const isLowerCase = str => str === str.toLowerCase();
 
isLowerCase('abc'); // true
 isLowerCase('a3@$'); // true
 isLowerCase('Ab4'); // false
-
beginner
isUpperCase
Checks if a string is upper case.
Convert the given string to upper case, using String.toUpperCase() and compare it to the original.
const isUpperCase = str => str === str.toUpperCase();
+
isUpperCase
Checks if a string is upper case.
Convert the given string to upper case, using String.toUpperCase() and compare it to the original.
const isUpperCase = str => str === str.toUpperCase();
 
isUpperCase('ABC'); // true
 isLowerCase('A3@$'); // true
 isLowerCase('aB4'); // false
-
beginner
mapString
Creates a new string with the results of calling a provided function on every character in the calling string.
Use String.split('') and Array.map() to call the provided function, fn, for each character in str. Use Array.join('') to recombine the array of characters into a string. The callback function, fn, takes three arguments (the current character, the index of the current character and the string mapString was called upon).
const mapString = (str, fn) =>
+
mapString
Creates a new string with the results of calling a provided function on every character in the calling string.
Use String.split('') and Array.map() to call the provided function, fn, for each character in str. Use Array.join('') to recombine the array of characters into a string. The callback function, fn, takes three arguments (the current character, the index of the current character and the string mapString was called upon).
const mapString = (str, fn) =>
   str
     .split('')
     .map((c, i) => fn(c, i, str))
     .join('');
 
mapString('lorem ipsum', c => c.toUpperCase()); // 'LOREM IPSUM'
-
intermediate
mask
Replaces all but the last num of characters with the specified mask character.
Use String.slice() to grab the portion of the characters that need to be masked and use String.replace() with a regexp to replace every character with the mask character. Concatenate the masked characters with the remaining unmasked portion of the string. Omit the second argument, num, to keep a default of 4 characters unmasked. If num is negative, the unmasked characters will be at the start of the string. Omit the third argument, mask, to use a default character of '*' for the mask.
const mask = (cc, num = 4, mask = '*') =>
+
mask
Replaces all but the last num of characters with the specified mask character.
Use String.slice() to grab the portion of the characters that need to be masked and use String.replace() with a regexp to replace every character with the mask character. Concatenate the masked characters with the remaining unmasked portion of the string. Omit the second argument, num, to keep a default of 4 characters unmasked. If num is negative, the unmasked characters will be at the start of the string. Omit the third argument, mask, to use a default character of '*' for the mask.
const mask = (cc, num = 4, mask = '*') =>
   ('' + cc).slice(0, -num).replace(/./g, mask) + ('' + cc).slice(-num);
 
mask(1234567890); // '******7890'
 mask(1234567890, 3); // '*******890'
 mask(1234567890, -4, '$'); // '$$$$567890'
-
beginner
pad
Pads a string on both sides with the specified character, if it's shorter than the specified length.
Use String.padStart() and String.padEnd() to pad both sides of the given string. Omit the third argument, char, to use the whitespace character as the default padding character.
const pad = (str, length, char = ' ') =>
+
pad
Pads a string on both sides with the specified character, if it's shorter than the specified length.
Use String.padStart() and String.padEnd() to pad both sides of the given string. Omit the third argument, char, to use the whitespace character as the default padding character.
const pad = (str, length, char = ' ') =>
   str.padStart((str.length + length) / 2, char).padEnd(length, char);
 
pad('cat', 8); // '  cat   '
 pad(String(42), 6, '0'); // '004200'
 pad('foobar', 3); // 'foobar'
-
intermediate
palindrome
Returns true if the given string is a palindrome, false otherwise.
Convert string String.toLowerCase() and use String.replace() to remove non-alphanumeric characters from it. Then, use the spread operator (...) to split string into individual characters, Array.reverse(), String.join('') and compare to the original, unreversed string, after converting it String.tolowerCase().
const palindrome = str => {
+
palindrome
Returns true if the given string is a palindrome, false otherwise.
Convert string String.toLowerCase() and use String.replace() to remove non-alphanumeric characters from it. Then, use the spread operator (...) to split string into individual characters, Array.reverse(), String.join('') and compare to the original, unreversed string, after converting it String.tolowerCase().
const palindrome = str => {
   const s = str.toLowerCase().replace(/[\W_]/g, '');
   return s === [...s].reverse().join('');
 };
 
palindrome('taco cat'); // true
-
intermediate
pluralize
Returns the singular or plural form of the word based on the input number. If the first argument is an object, it will use a closure by returning a function that can auto-pluralize words that don't simply end in s if the supplied dictionary contains the word.
If num is either -1 or 1, return the singular form of the word. If num is any other number, return the plural form. Omit the third argument to use the default of the singular word + s, or supply a custom pluralized word when necessary. If the first argument is an object, utilize a closure by returning a function which can use the supplied dictionary to resolve the correct plural form of the word.
const pluralize = (val, word, plural = word + 's') => {
+
pluralize
Returns the singular or plural form of the word based on the input number. If the first argument is an object, it will use a closure by returning a function that can auto-pluralize words that don't simply end in s if the supplied dictionary contains the word.
If num is either -1 or 1, return the singular form of the word. If num is any other number, return the plural form. Omit the third argument to use the default of the singular word + s, or supply a custom pluralized word when necessary. If the first argument is an object, utilize a closure by returning a function which can use the supplied dictionary to resolve the correct plural form of the word.
const pluralize = (val, word, plural = word + 's') => {
   const _pluralize = (num, word, plural = word + 's') =>
     [1, -1].includes(Number(num)) ? word : plural;
   if (typeof val === 'object') return (num, word) => _pluralize(num, word, val[word]);
@@ -190,15 +190,15 @@
 };
 const autoPluralize = pluralize(PLURALS);
 autoPluralize(2, 'person'); // 'people'
-
intermediate
removeNonASCII
Removes non-printable ASCII characters.
Use a regular expression to remove non-printable ASCII characters.
const removeNonASCII = str => str.replace(/[^\x20-\x7E]/g, '');
+
removeNonASCII
Removes non-printable ASCII characters.
Use a regular expression to remove non-printable ASCII characters.
const removeNonASCII = str => str.replace(/[^\x20-\x7E]/g, '');
 
removeNonASCII('äÄçÇéÉêlorem-ipsumöÖÐþúÚ'); // 'lorem-ipsum'
-
beginner
reverseString
Reverses a string.
Use the spread operator (...) and Array.reverse() to reverse the order of the characters in the string. Combine characters to get a string using String.join('').
const reverseString = str => [...str].reverse().join('');
+
reverseString
Reverses a string.
Use the spread operator (...) and Array.reverse() to reverse the order of the characters in the string. Combine characters to get a string using String.join('').
const reverseString = str => [...str].reverse().join('');
 
reverseString('foobar'); // 'raboof'
-
beginner
sortCharactersInString
Alphabetically sorts the characters in a string.
Use the spread operator (...), Array.sort() and String.localeCompare() to sort the characters in str, recombine using String.join('').
const sortCharactersInString = str => [...str].sort((a, b) => a.localeCompare(b)).join('');
+
sortCharactersInString
Alphabetically sorts the characters in a string.
Use the spread operator (...), Array.sort() and String.localeCompare() to sort the characters in str, recombine using String.join('').
const sortCharactersInString = str => [...str].sort((a, b) => a.localeCompare(b)).join('');
 
sortCharactersInString('cabbage'); // 'aabbceg'
-
beginner
splitLines
Splits a multiline string into an array of lines.
Use String.split() and a regular expression to match line breaks and create an array.
const splitLines = str => str.split(/\r?\n/);
+
splitLines
Splits a multiline string into an array of lines.
Use String.split() and a regular expression to match line breaks and create an array.
const splitLines = str => str.split(/\r?\n/);
 
splitLines('This\nis a\nmultiline\nstring.\n'); // ['This', 'is a', 'multiline', 'string.' , '']
-
advanced
stringPermutations
⚠️ WARNING: This function's execution time increases exponentially with each character. Anything more than 8 to 10 characters will cause your browser to hang as it tries to solve all the different combinations.
Generates all permutations of a string (contains duplicates).
Use recursion. For each letter in the given string, create all the partial permutations for the rest of its letters. Use Array.map() to combine the letter with each partial permutation, then Array.reduce() to combine all permutations in one array. Base cases are for string length equal to 2 or 1.
const stringPermutations = str => {
+
stringPermutations
⚠️ WARNING: This function's execution time increases exponentially with each character. Anything more than 8 to 10 characters will cause your browser to hang as it tries to solve all the different combinations.
Generates all permutations of a string (contains duplicates).
Use recursion. For each letter in the given string, create all the partial permutations for the rest of its letters. Use Array.map() to combine the letter with each partial permutation, then Array.reduce() to combine all permutations in one array. Base cases are for string length equal to 2 or 1.
const stringPermutations = str => {
   if (str.length <= 2) return str.length === 2 ? [str, str[1] + str[0]] : [str];
   return str
     .split('')
@@ -209,9 +209,9 @@
     );
 };
 
stringPermutations('abc'); // ['abc','acb','bac','bca','cab','cba']
-
beginner
stripHTMLTags
Removes HTML/XML tags from string.
Use a regular expression to remove HTML/XML tags from a string.
const stripHTMLTags = str => str.replace(/<[^>]*>/g, '');
+
stripHTMLTags
Removes HTML/XML tags from string.
Use a regular expression to remove HTML/XML tags from a string.
const stripHTMLTags = str => str.replace(/<[^>]*>/g, '');
 
stripHTMLTags('<p><em>lorem</em> <strong>ipsum</strong></p>'); // 'lorem ipsum'
-
intermediate
toCamelCase
Converts a string to camelcase.
Break the string into words and combine them capitalizing the first letter of each word, using a regexp.
const toCamelCase = str => {
+
toCamelCase
Converts a string to camelcase.
Break the string into words and combine them capitalizing the first letter of each word, using a regexp.
const toCamelCase = str => {
   let s =
     str &&
     str
@@ -224,7 +224,7 @@
 toCamelCase('Some label that needs to be camelized'); // 'someLabelThatNeedsToBeCamelized'
 toCamelCase('some-javascript-property'); // 'someJavascriptProperty'
 toCamelCase('some-mixed_string with spaces_underscores-and-hyphens'); // 'someMixedStringWithSpacesUnderscoresAndHyphens'
-
intermediate
toKebabCase
Converts a string to kebab case.
Break the string into words and combine them adding - as a separator, using a regexp.
const toKebabCase = str =>
+
toKebabCase
Converts a string to kebab case.
Break the string into words and combine them adding - as a separator, using a regexp.
const toKebabCase = str =>
   str &&
   str
     .match(/[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g)
@@ -235,7 +235,7 @@
 toKebabCase('some-mixed_string With spaces_underscores-and-hyphens'); // 'some-mixed-string-with-spaces-underscores-and-hyphens'
 toKebabCase('AllThe-small Things'); // "all-the-small-things"
 toKebabCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML'); // "i-am-listening-to-fm-while-loading-different-url-on-my-browser-and-also-editing-xml-and-html"
-
intermediate
toSnakeCase
Converts a string to snake case.
Break the string into words and combine them adding _ as a separator, using a regexp.
const toSnakeCase = str =>
+
toSnakeCase
Converts a string to snake case.
Break the string into words and combine them adding _ as a separator, using a regexp.
const toSnakeCase = str =>
   str &&
   str
     .match(/[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g)
@@ -246,10 +246,10 @@
 toSnakeCase('some-mixed_string With spaces_underscores-and-hyphens'); // 'some_mixed_string_with_spaces_underscores_and_hyphens'
 toSnakeCase('AllThe-small Things'); // "all_the_smal_things"
 toSnakeCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML'); // "i_am_listening_to_fm_while_loading_different_url_on_my_browser_and_also_editing_some_xml_and_html"
-
beginner
truncateString
Truncates a string up to a specified length.
Determine if the string's length is greater than num. Return the string truncated to the desired length, with '...' appended to the end or the original string.
const truncateString = (str, num) =>
+
truncateString
Truncates a string up to a specified length.
Determine if the string's length is greater than num. Return the string truncated to the desired length, with '...' appended to the end or the original string.
const truncateString = (str, num) =>
   str.length > num ? str.slice(0, num > 3 ? num - 3 : num) + '...' : str;
 
truncateString('boomerang', 7); // 'boom...'
-
beginner
unescapeHTML
Unescapes escaped HTML characters.
Use String.replace() with a regex that matches the characters that need to be unescaped, using a callback function to replace each escaped character instance with its associated unescaped character using a dictionary (object).
const unescapeHTML = str =>
+
unescapeHTML
Unescapes escaped HTML characters.
Use String.replace() with a regex that matches the characters that need to be unescaped, using a callback function to replace each escaped character instance with its associated unescaped character using a dictionary (object).
const unescapeHTML = str =>
   str.replace(
     /&amp;|&lt;|&gt;|&#39;|&quot;/g,
     tag =>
@@ -262,7 +262,7 @@
       }[tag] || tag)
   );
 
unescapeHTML('&lt;a href=&quot;#&quot;&gt;Me &amp; you&lt;/a&gt;'); // '<a href="#">Me & you</a>'
-
advanced
URLJoin
Joins all given URL segments together, then normalizes the resulting URL.
Use String.join('/') to combine URL segments, then a series of String.replace() calls with various regexps to normalize the resulting URL (remove double slashes, add proper slashes for protocol, remove slashes before parameters, combine parameters with '&' and normalize first parameter delimiter).
const URLJoin = (...args) =>
+
URLJoin
Joins all given URL segments together, then normalizes the resulting URL.
Use String.join('/') to combine URL segments, then a series of String.replace() calls with various regexps to normalize the resulting URL (remove double slashes, add proper slashes for protocol, remove slashes before parameters, combine parameters with '&' and normalize first parameter delimiter).
const URLJoin = (...args) =>
   args
     .join('/')
     .replace(/[\/]+/g, '/')
@@ -272,7 +272,7 @@
     .replace(/\?/g, '&')
     .replace('&', '?');
 
URLJoin('http://www.google.com', 'a', '/b/cd', '?foo=123', '?bar=foo'); // 'http://www.google.com/a/b/cd?foo=123&bar=foo'
-
intermediate
words
Converts a given string into an array of words.
Use String.split() with a supplied pattern (defaults to non-alpha as a regexp) to convert to an array of strings. Use Array.filter() to remove any empty strings. Omit the second argument to use the default regexp.
const words = (str, pattern = /[^a-zA-Z-]+/) => str.split(pattern).filter(Boolean);
+
words
Converts a given string into an array of words.
Use String.split() with a supplied pattern (defaults to non-alpha as a regexp) to convert to an array of strings. Use Array.filter() to remove any empty strings. Omit the second argument to use the default regexp.
const words = (str, pattern = /[^a-zA-Z-]+/) => str.split(pattern).filter(Boolean);
 
words('I love javaScript!!'); // ["I", "love", "javaScript"]
 words('python, javaScript & coffee'); // ["python", "javaScript", "coffee"]
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/style.css b/docs/style.css index 096ce23da..a656cdbb2 100644 --- a/docs/style.css +++ b/docs/style.css @@ -1 +1 @@ -@font-face{font-family:'Roboto';font-style:normal;font-weight:300;src:local("Roboto Light"),local("Roboto-Light"),url(https://fonts.gstatic.com/s/roboto/v18/KFOlCnqEu92Fr1MmSU5fBBc4.woff2) format("woff2");unicode-range:U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;font-display:swap}@font-face{font-family:'Roboto';font-style:italic;font-weight:300;src:local("Roboto Light Italic"),local("Roboto-LightItalic"),url(https://fonts.gstatic.com/s/roboto/v18/KFOjCnqEu92Fr1Mu51TjASc6CsQ.woff2) format("woff2");unicode-range:U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;font-display:swap}@font-face{font-family:'Roboto';font-style:normal;font-weight:500;src:local("Roboto Medium"),local("Roboto-Medium"),url(https://fonts.gstatic.com/s/roboto/v18/KFOlCnqEu92Fr1MmEU9fBBc4.woff2) format("woff2");unicode-range:U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;font-display:swap}@font-face{font-family:'Roboto Mono';font-style:normal;font-weight:300;src:local("Roboto Mono Light"),local("RobotoMono-Light"),url(https://fonts.gstatic.com/s/robotomono/v5/L0xkDF4xlVMF-BfR8bXMIjDgiWqxf78.woff2) format("woff2");unicode-range:U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;font-display:swap}@font-face{font-family:'Roboto Mono';font-style:italic;font-weight:300;src:local("Roboto Mono Light 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.collapse.toggled{background-image:url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%23607D8B' stroke-width='2' stroke-linecap='round' stroke-linejoin='round' class='feather feather-minus-square'%3E%3Crect x='3' y='3' width='18' height='18' rx='2' ry='2'%3E%3C/rect%3E%3Cline x1='8' y1='12' x2='16' y2='12'%3E%3C/line%3E%3C/svg%3E");padding-bottom:calc(0.125 * var(--universal-padding))}.card.code-card .collapse.toggled+pre.card-examples{position:relative;transform:scaleY(1)}.card.code-card pre.section.card-code{position:relative;margin-bottom:0;padding-bottom:0;padding-top:calc(3 * var(--universal-padding))}.card.code-card pre.section.card-examples{margin-top:0;margin-bottom:0;border-radius:0 0 calc(4 * var(--universal-border-radius)) calc(4 * var(--universal-border-radius));padding-top:0}.card.code-card pre.section.card-examples:before{content:'';display:block;position:absolute;top:0;left:0.5625rem;border-left:.0625rem solid var(--collapse-color);height:calc(100% - 18px)}.card.code-card .copy-button-container{position:relative;z-index:2}.card.code-card .copy-button-container .copy-button{background:var(--copy-button-color);box-sizing:border-box;position:absolute;top:-1.75rem;right:0;margin:calc(2 * var(--universal-margin));padding:calc(2.5 * var(--universal-padding));border-radius:50%;border:0;box-shadow:0 2px 2px 0 rgba(0,0,0,0.14),0 3px 1px -2px rgba(0,0,0,0.12),0 1px 5px 0 rgba(0,0,0,0.2);transition:all 0.3s ease;cursor:pointer;background-image:url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%23f0f0f0' stroke-width='2' stroke-linecap='round' stroke-linejoin='round' class='feather feather-clipboard'%3E%3Cpath d='M16 4h2a2 2 0 0 1 2 2v14a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2V6a2 2 0 0 1 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3px 1px -2px rgba(0,0,0,0.06),0 1px 5px 0 rgba(0,0,0,0.1)}.card.code-card .corner.beginner{background:var(--beginner-color)}.card.code-card .corner.intermediate{background:var(--intermediate-color)}.card.code-card .corner.advanced{background:var(--advanced-color)}.toast{position:fixed;bottom:calc(var(--universal-margin) * 2);margin-bottom:0;font-size:0.8125rem;left:50%;transform:translate(-50%, -50%);z-index:1111;color:var(--back-color);background:var(--fore-color);border-radius:calc(var(--universal-border-radius) * 16);padding:var(--universal-padding) calc(var(--universal-padding) * 2);box-shadow:0 2px 2px 0 rgba(0,0,0,0.14),0 3px 1px -2px rgba(0,0,0,0.12),0 1px 5px 0 rgba(0,0,0,0.2);transition:all 0.3s ease}header{box-sizing:border-box;overflow:hidden;height:3.5rem;position:fixed;width:110%;top:0;left:-5%;box-shadow:0 2px 4px rgba(0,0,0,0.5);z-index:5;background:var(--header-back-color);transition:top 0.3s ease}header 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a:visited{color:var(--nav-link-fore-color)}[type="search"]{color:var(--search-fore-color);background:var(--search-back-color);outline:none;box-sizing:border-box;border:none;border-bottom:.0625rem solid var(--search-border-color);width:100%;margin-bottom:var(--universal-margin);padding:calc(2 * var(--universal-padding)) calc(1.5 * var(--universal-padding)) var(--universal-padding) calc(1.5 * var(--universal-padding));transition:all 0.3s ease}[type="search"]:hover,[type="search"]:focus{border-bottom:.0625rem solid var(--search-hover-border-color)}[type="search"]:focus{box-shadow:0 .0625rem 0 0 var(--search-hover-border-color)}.menu-button{position:fixed;top:0;left:0;z-index:1000;box-sizing:border-box;height:3.5rem;width:3.5rem;border:0;background:transparent;background-image:url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%23fafafa' stroke-width='2' stroke-linecap='round' stroke-linejoin='round' 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a:visited{color:var(--nav-link-fore-color)}[type="search"]{color:var(--search-fore-color);background:var(--search-back-color);outline:none;box-sizing:border-box;border:none;border-bottom:.0625rem solid var(--search-border-color);width:100%;margin-bottom:var(--universal-margin);padding:calc(2 * var(--universal-padding)) calc(1.5 * var(--universal-padding)) var(--universal-padding) calc(1.5 * var(--universal-padding));transition:all 0.3s ease}[type="search"]:hover,[type="search"]:focus{border-bottom:.0625rem solid var(--search-hover-border-color)}[type="search"]:focus{box-shadow:0 .0625rem 0 0 var(--search-hover-border-color)}.menu-button{position:fixed;top:0;left:0;z-index:1000;box-sizing:border-box;height:3.5rem;width:3.5rem;border:0;background:transparent;background-image:url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%23fafafa' stroke-width='2' stroke-linecap='round' stroke-linejoin='round' class='feather feather-more-horizontal'%3E%3Ccircle cx='12' cy='12' r='1'%3E%3C/circle%3E%3Ccircle cx='19' cy='12' r='1'%3E%3C/circle%3E%3Ccircle cx='5' cy='12' r='1'%3E%3C/circle%3E%3C/svg%3E");background-repeat:no-repeat;background-position:0.875rem 0.875rem;cursor:pointer;transition:all 0.3s ease}.menu-button:hover{background-color:rgba(255,255,255,0.08)}.menu-button.toggled{background-image:url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%23fafafa' stroke-width='2' stroke-linecap='round' stroke-linejoin='round' class='feather feather-more-vertical'%3E%3Ccircle cx='12' cy='12' r='1'%3E%3C/circle%3E%3Ccircle cx='12' cy='5' r='1'%3E%3C/circle%3E%3Ccircle cx='12' cy='19' r='1'%3E%3C/circle%3E%3C/svg%3E")}footer{color:var(--footer-fore-color);background:var(--footer-back-color);padding-top:calc(2 * var(--universal-padding));padding-bottom:calc(3 * var(--universal-padding));margin-top:calc(6 * var(--universal-margin))}footer *{font-size:0.875rem}footer a,footer a:link,footer a:visited{color:var(--fore-color)}.scroll-to-top{position:fixed;bottom:1rem;right:1.3125rem;box-sizing:border-box;z-index:1100;height:2.75rem;width:2.75rem;border:0;border-radius:100%;background:var(--scrolltop-button-color);background-image:url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%23f0f0f0' stroke-width='2' stroke-linecap='round' stroke-linejoin='round' class='feather feather-arrow-up'%3E%3Cline x1='12' y1='19' x2='12' y2='5'%3E%3C/line%3E%3Cpolyline points='5 12 12 5 19 12'%3E%3C/polyline%3E%3C/svg%3E");background-repeat:no-repeat;background-position:center center;cursor:pointer;box-shadow:0 2px 2px 0 rgba(0,0,0,0.14),0 3px 1px -2px rgba(0,0,0,0.12),0 1px 5px 0 rgba(0,0,0,0.2);transition:all 0.3s ease}.scroll-to-top:hover,.scroll-to-top:focus{background-color:var(--scrolltop-button-hover-color);box-shadow:0 3px 3px 0 rgba(0,0,0,0.14),0 1px 7px 0 rgba(0,0,0,0.12),0 3px 1px -1px rgba(0,0,0,0.2)}.card.contributor>.section.button{font-size:1rem;font-weight:500;text-align:center;display:block;transition:all 0.3s ease}.card.contributor>.section.button:link,.card.contributor>.section.button:visited{color:var(--fore-color)}.card.contributor>.section.button:link:hover,.card.contributor>.section.button:visited:hover{color:var(--a-link-color);text-decoration:none} diff --git a/docs/type.html b/docs/type.html index 43d5ece6a..8dd03726c 100644 --- a/docs/type.html +++ b/docs/type.html @@ -73,10 +73,10 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Type

beginner

getType

Returns the native type of a value.

Returns lowercased constructor name of value, "undefined" or "null" if value is undefined or null.

const getType = v =>
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Type
getType
Returns the native type of a value.
Returns lowercased constructor name of value, "undefined" or "null" if value is undefined or null.
const getType = v =>
   v === undefined ? 'undefined' : v === null ? 'null' : v.constructor.name.toLowerCase();
 
getType(new Set([1, 2, 3])); // 'set'
-
beginner
is
Checks if the provided value is of the specified type.
Ensure the value is not undefined or null using Array.includes(), and compare the constructor property on the value with type to check if the provided value is of the specified type.
const is = (type, val) => ![, null].includes(val) && val.constructor === type;
+
is
Checks if the provided value is of the specified type.
Ensure the value is not undefined or null using Array.includes(), and compare the constructor property on the value with type to check if the provided value is of the specified type.
const is = (type, val) => ![, null].includes(val) && val.constructor === type;
 
is(Array, [1]); // true
 is(ArrayBuffer, new ArrayBuffer()); // true
 is(Map, new Map()); // true
@@ -90,14 +90,14 @@
 is(Number, new Number(1)); // true
 is(Boolean, true); // true
 is(Boolean, new Boolean(true)); // true
-
intermediate
isArrayLike
Checks if the provided argument is array-like (i.e. is iterable).
Check if the provided argument is not null and that its Symbol.iterator property is a function.
const isArrayLike = obj => obj != null && typeof obj[Symbol.iterator] === 'function';
+
isArrayLike
Checks if the provided argument is array-like (i.e. is iterable).
Check if the provided argument is not null and that its Symbol.iterator property is a function.
const isArrayLike = obj => obj != null && typeof obj[Symbol.iterator] === 'function';
 
isArrayLike(document.querySelectorAll('.className')); // true
 isArrayLike('abc'); // true
 isArrayLike(null); // false
-
beginner
isBoolean
Checks if the given argument is a native boolean element.
Use typeof to check if a value is classified as a boolean primitive.
const isBoolean = val => typeof val === 'boolean';
+
isBoolean
Checks if the given argument is a native boolean element.
Use typeof to check if a value is classified as a boolean primitive.
const isBoolean = val => typeof val === 'boolean';
 
isBoolean(null); // false
 isBoolean(false); // true
-
beginner
isEmpty
Returns true if the a value is an empty object, collection, map or set, has no enumerable properties or is any type that is not considered a collection.
Check if the provided value is null or if its length is equal to 0.
const isEmpty = val => val == null || !(Object.keys(val) || val).length;
+
isEmpty
Returns true if the a value is an empty object, collection, map or set, has no enumerable properties or is any type that is not considered a collection.
Check if the provided value is null or if its length is equal to 0.
const isEmpty = val => val == null || !(Object.keys(val) || val).length;
 
isEmpty(new Map()); // true
 isEmpty(new Set()); // true
 isEmpty([]); // true
@@ -108,40 +108,40 @@
 isEmpty('text'); // false
 isEmpty(123); // true - type is not considered a collection
 isEmpty(true); // true - type is not considered a collection
-
beginner
isFunction
Checks if the given argument is a function.
Use typeof to check if a value is classified as a function primitive.
const isFunction = val => typeof val === 'function';
+
isFunction
Checks if the given argument is a function.
Use typeof to check if a value is classified as a function primitive.
const isFunction = val => typeof val === 'function';
 
isFunction('x'); // false
 isFunction(x => x); // true
-
beginner
isNil
Returns true if the specified value is null or undefined, false otherwise.
Use the strict equality operator to check if the value and of val are equal to null or undefined.
const isNil = val => val === undefined || val === null;
+
isNil
Returns true if the specified value is null or undefined, false otherwise.
Use the strict equality operator to check if the value and of val are equal to null or undefined.
const isNil = val => val === undefined || val === null;
 
isNil(null); // true
 isNil(undefined); // true
-
beginner
isNull
Returns true if the specified value is null, false otherwise.
Use the strict equality operator to check if the value and of val are equal to null.
const isNull = val => val === null;
+
isNull
Returns true if the specified value is null, false otherwise.
Use the strict equality operator to check if the value and of val are equal to null.
const isNull = val => val === null;
 
isNull(null); // true
-
beginner
isNumber
Checks if the given argument is a number.
Use typeof to check if a value is classified as a number primitive.
const isNumber = val => typeof val === 'number';
+
isNumber
Checks if the given argument is a number.
Use typeof to check if a value is classified as a number primitive.
const isNumber = val => typeof val === 'number';
 
isNumber('1'); // false
 isNumber(1); // true
-
beginner
isObject
Returns a boolean determining if the passed value is an object or not.
Uses the Object constructor to create an object wrapper for the given value. If the value is null or undefined, create and return an empty object. Οtherwise, return an object of a type that corresponds to the given value.
const isObject = obj => obj === Object(obj);
+
isObject
Returns a boolean determining if the passed value is an object or not.
Uses the Object constructor to create an object wrapper for the given value. If the value is null or undefined, create and return an empty object. Οtherwise, return an object of a type that corresponds to the given value.
const isObject = obj => obj === Object(obj);
 
isObject([1, 2, 3, 4]); // true
 isObject([]); // true
 isObject(['Hello!']); // true
 isObject({ a: 1 }); // true
 isObject({}); // true
 isObject(true); // false
-
beginner
isObjectLike
Checks if a value is object-like.
Check if the provided value is not null and its typeof is equal to 'object'.
const isObjectLike = val => val !== null && typeof val === 'object';
+
isObjectLike
Checks if a value is object-like.
Check if the provided value is not null and its typeof is equal to 'object'.
const isObjectLike = val => val !== null && typeof val === 'object';
 
isObjectLike({}); // true
 isObjectLike([1, 2, 3]); // true
 isObjectLike(x => x); // false
 isObjectLike(null); // false
-
intermediate
isPlainObject
Checks if the provided value is an object created by the Object constructor.
Check if the provided value is truthy, use typeof to check if it is an object and Object.constructor to make sure the constructor is equal to Object.
const isPlainObject = val => !!val && typeof val === 'object' && val.constructor === Object;
+
isPlainObject
Checks if the provided value is an object created by the Object constructor.
Check if the provided value is truthy, use typeof to check if it is an object and Object.constructor to make sure the constructor is equal to Object.
const isPlainObject = val => !!val && typeof val === 'object' && val.constructor === Object;
 
isPlainObject({ a: 1 }); // true
 isPlainObject(new Map()); // false
-
intermediate
isPrimitive
Returns a boolean determining if the passed value is primitive or not.
Use Array.includes() on an array of type strings which are not primitive, supplying the type using typeof. Since typeof null evaluates to 'object', it needs to be directly compared.
const isPrimitive = val => !['object', 'function'].includes(typeof val) || val === null;
+
isPrimitive
Returns a boolean determining if the passed value is primitive or not.
Use Array.includes() on an array of type strings which are not primitive, supplying the type using typeof. Since typeof null evaluates to 'object', it needs to be directly compared.
const isPrimitive = val => !['object', 'function'].includes(typeof val) || val === null;
 
isPrimitive(null); // true
 isPrimitive(50); // true
 isPrimitive('Hello!'); // true
 isPrimitive(false); // true
 isPrimitive(Symbol()); // true
 isPrimitive([]); // false
-
intermediate
isPromiseLike
Returns true if an object looks like a Promise, false otherwise.
Check if the object is not null, its typeof matches either object or function and if it has a .then property, which is also a function.
const isPromiseLike = obj =>
+
isPromiseLike
Returns true if an object looks like a Promise, false otherwise.
Check if the object is not null, its typeof matches either object or function and if it has a .then property, which is also a function.
const isPromiseLike = obj =>
   obj !== null &&
   (typeof obj === 'object' || typeof obj === 'function') &&
   typeof obj.then === 'function';
@@ -152,13 +152,13 @@
 }); // true
 isPromiseLike(null); // false
 isPromiseLike({}); // false
-
beginner
isString
Checks if the given argument is a string.
Use typeof to check if a value is classified as a string primitive.
const isString = val => typeof val === 'string';
+
isString
Checks if the given argument is a string.
Use typeof to check if a value is classified as a string primitive.
const isString = val => typeof val === 'string';
 
isString('10'); // true
-
beginner
isSymbol
Checks if the given argument is a symbol.
Use typeof to check if a value is classified as a symbol primitive.
const isSymbol = val => typeof val === 'symbol';
+
isSymbol
Checks if the given argument is a symbol.
Use typeof to check if a value is classified as a symbol primitive.
const isSymbol = val => typeof val === 'symbol';
 
isSymbol(Symbol('x')); // true
-
beginner
isUndefined
Returns true if the specified value is undefined, false otherwise.
Use the strict equality operator to check if the value and of val are equal to undefined.
const isUndefined = val => val === undefined;
+
isUndefined
Returns true if the specified value is undefined, false otherwise.
Use the strict equality operator to check if the value and of val are equal to undefined.
const isUndefined = val => val === undefined;
 
isUndefined(undefined); // true
-
intermediate
isValidJSON
Checks if the provided argument is a valid JSON.
Use JSON.parse() and a try... catch block to check if the provided argument is a valid JSON.
const isValidJSON = obj => {
+
isValidJSON
Checks if the provided argument is a valid JSON.
Use JSON.parse() and a try... catch block to check if the provided argument is a valid JSON.
const isValidJSON = obj => {
   try {
     JSON.parse(obj);
     return true;
@@ -169,4 +169,4 @@
 
isValidJSON('{"name":"Adam","age":20}'); // true
 isValidJSON('{"name":"Adam",age:"20"}'); // false
 isValidJSON(null); // true
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/docs/utility.html b/docs/utility.html index 5db21f79b..e7680aae4 100644 --- a/docs/utility.html +++ b/docs/utility.html @@ -73,18 +73,18 @@ },1700); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.



Utility

beginner

castArray

Casts the provided value as an array if it's not one.

Use Array.isArray() to determine if val is an array and return it as-is or encapsulated in an array accordingly.

const castArray = val => (Array.isArray(val) ? val : [val]);
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.


Utility
castArray
Casts the provided value as an array if it's not one.
Use Array.isArray() to determine if val is an array and return it as-is or encapsulated in an array accordingly.
const castArray = val => (Array.isArray(val) ? val : [val]);
 
castArray('foo'); // ['foo']
 castArray([1]); // [1]
-
intermediate
cloneRegExp
Clones a regular expression.
Use new RegExp(), RegExp.source and RegExp.flags to clone the given regular expression.
const cloneRegExp = regExp => new RegExp(regExp.source, regExp.flags);
+
cloneRegExp
Clones a regular expression.
Use new RegExp(), RegExp.source and RegExp.flags to clone the given regular expression.
const cloneRegExp = regExp => new RegExp(regExp.source, regExp.flags);
 
const regExp = /lorem ipsum/gi;
 const regExp2 = cloneRegExp(regExp); // /lorem ipsum/gi
-
beginner
coalesce
Returns the first non-null/undefined argument.
Use Array.find() to return the first non null/undefined argument.
const coalesce = (...args) => args.find(_ => ![undefined, null].includes(_));
+
coalesce
Returns the first non-null/undefined argument.
Use Array.find() to return the first non null/undefined argument.
const coalesce = (...args) => args.find(_ => ![undefined, null].includes(_));
 
coalesce(null, undefined, '', NaN, 'Waldo'); // ""
-
intermediate
coalesceFactory
Returns a customized coalesce function that returns the first argument that returns true from the provided argument validation function.
Use Array.find() to return the first argument that returns true from the provided argument validation function.
const coalesceFactory = valid => (...args) => args.find(valid);
+
coalesceFactory
Returns a customized coalesce function that returns the first argument that returns true from the provided argument validation function.
Use Array.find() to return the first argument that returns true from the provided argument validation function.
const coalesceFactory = valid => (...args) => args.find(valid);
 
const customCoalesce = coalesceFactory(_ => ![null, undefined, '', NaN].includes(_));
 customCoalesce(undefined, null, NaN, '', 'Waldo'); // "Waldo"
-
intermediate
extendHex
Extends a 3-digit color code to a 6-digit color code.
Use Array.map(), String.split() and Array.join() to join the mapped array for converting a 3-digit RGB notated hexadecimal color-code to the 6-digit form. Array.slice() is used to remove # from string start since it's added once.
const extendHex = shortHex =>
+
extendHex
Extends a 3-digit color code to a 6-digit color code.
Use Array.map(), String.split() and Array.join() to join the mapped array for converting a 3-digit RGB notated hexadecimal color-code to the 6-digit form. Array.slice() is used to remove # from string start since it's added once.
const extendHex = shortHex =>
   '#' +
   shortHex
     .slice(shortHex.startsWith('#') ? 1 : 0)
@@ -93,14 +93,14 @@
     .join('');
 
extendHex('#03f'); // '#0033ff'
 extendHex('05a'); // '#0055aa'
-
intermediate
getURLParameters
Returns an object containing the parameters of the current URL.
Use String.match() with an appropriate regular expression to get all key-value pairs, Array.reduce() to map and combine them into a single object. Pass location.search as the argument to apply to the current url.
const getURLParameters = url =>
+
getURLParameters
Returns an object containing the parameters of the current URL.
Use String.match() with an appropriate regular expression to get all key-value pairs, Array.reduce() to map and combine them into a single object. Pass location.search as the argument to apply to the current url.
const getURLParameters = url =>
   (url.match(/([^?=&]+)(=([^&]*))/g) || []).reduce(
     (a, v) => ((a[v.slice(0, v.indexOf('='))] = v.slice(v.indexOf('=') + 1)), a),
     {}
   );
 
getURLParameters('http://url.com/page?name=Adam&surname=Smith'); // {name: 'Adam', surname: 'Smith'}
 getURLParameters('google.com'); // {}
-
advanced
hexToRGB
Converts a color code to a rgb() or rgba() string if alpha value is provided.
Use bitwise right-shift operator and mask bits with & (and) operator to convert a hexadecimal color code (with or without prefixed with #) to a string with the RGB values. If it's 3-digit color code, first convert to 6-digit version. If an alpha value is provided alongside 6-digit hex, give rgba() string in return.
const hexToRGB = hex => {
+
hexToRGB
Converts a color code to a rgb() or rgba() string if alpha value is provided.
Use bitwise right-shift operator and mask bits with & (and) operator to convert a hexadecimal color code (with or without prefixed with #) to a string with the RGB values. If it's 3-digit color code, first convert to 6-digit version. If an alpha value is provided alongside 6-digit hex, give rgba() string in return.
const hexToRGB = hex => {
   let alpha = false,
     h = hex.slice(hex.startsWith('#') ? 1 : 0);
   if (h.length === 3) h = [...h].map(x => x + x).join('');
@@ -122,7 +122,7 @@
 
hexToRGB('#27ae60ff'); // 'rgba(39, 174, 96, 255)'
 hexToRGB('27ae60'); // 'rgb(39, 174, 96)'
 hexToRGB('#fff'); // 'rgb(255, 255, 255)'
-
intermediate
httpGet
Makes a GET request to the passed URL.
Use XMLHttpRequest web api to make a get request to the given url. Handle the onload event, by calling the given callback the responseText. Handle the onerror event, by running the provided err function. Omit the third argument, err, to log errors to the console's error stream by default.
const httpGet = (url, callback, err = console.error) => {
+
httpGet
Makes a GET request to the passed URL.
Use XMLHttpRequest web api to make a get request to the given url. Handle the onload event, by calling the given callback the responseText. Handle the onerror event, by running the provided err function. Omit the third argument, err, to log errors to the console's error stream by default.
const httpGet = (url, callback, err = console.error) => {
   const request = new XMLHttpRequest();
   request.open('GET', url, true);
   request.onload = () => callback(request.responseText);
@@ -140,7 +140,7 @@ Logs: {
   "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"
 }
 */
-
intermediate
httpPost
Makes a POST request to the passed URL.
Use XMLHttpRequest web api to make a post request to the given url. Set the value of an HTTP request header with setRequestHeader method. Handle the onload event, by calling the given callback the responseText. Handle the onerror event, by running the provided err function. Omit the third argument, data, to send no data to the provided url. Omit the fourth argument, err, to log errors to the console's error stream by default.
const httpPost = (url, data, callback, err = console.error) => {
+
httpPost
Makes a POST request to the passed URL.
Use XMLHttpRequest web api to make a post request to the given url. Set the value of an HTTP request header with setRequestHeader method. Handle the onload event, by calling the given callback the responseText. Handle the onerror event, by running the provided err function. Omit the third argument, data, to send no data to the provided url. Omit the fourth argument, err, to log errors to the console's error stream by default.
const httpPost = (url, data, callback, err = console.error) => {
   const request = new XMLHttpRequest();
   request.open('POST', url, true);
   request.setRequestHeader('Content-type', 'application/json; charset=utf-8');
@@ -176,10 +176,10 @@ Logs: {
   "id": 101
 }
 */
-
intermediate
isBrowser
Determines if the current runtime environment is a browser so that front-end modules can run on the server (Node) without throwing errors.
Use Array.includes() on the typeof values of both window and document (globals usually only available in a browser environment unless they were explicitly defined), which will return true if one of them is undefined. typeof allows globals to be checked for existence without throwing a ReferenceError. If both of them are not undefined, then the current environment is assumed to be a browser.
const isBrowser = () => ![typeof window, typeof document].includes('undefined');
+
isBrowser
Determines if the current runtime environment is a browser so that front-end modules can run on the server (Node) without throwing errors.
Use Array.includes() on the typeof values of both window and document (globals usually only available in a browser environment unless they were explicitly defined), which will return true if one of them is undefined. typeof allows globals to be checked for existence without throwing a ReferenceError. If both of them are not undefined, then the current environment is assumed to be a browser.
const isBrowser = () => ![typeof window, typeof document].includes('undefined');
 
isBrowser(); // true (browser)
 isBrowser(); // false (Node)
-
intermediate
mostPerformant
Returns the index of the function in an array of functions which executed the fastest.
Use Array.map() to generate an array where each value is the total time taken to execute the function after iterations times. Use the difference in performance.now() values before and after to get the total time in milliseconds to a high degree of accuracy. Use Math.min() to find the minimum execution time, and return the index of that shortest time which corresponds to the index of the most performant function. Omit the second argument, iterations, to use a default of 10,000 iterations. The more iterations, the more reliable the result but the longer it will take.
const mostPerformant = (fns, iterations = 10000) => {
+
mostPerformant
Returns the index of the function in an array of functions which executed the fastest.
Use Array.map() to generate an array where each value is the total time taken to execute the function after iterations times. Use the difference in performance.now() values before and after to get the total time in milliseconds to a high degree of accuracy. Use Math.min() to find the minimum execution time, and return the index of that shortest time which corresponds to the index of the most performant function. Omit the second argument, iterations, to use a default of 10,000 iterations. The more iterations, the more reliable the result but the longer it will take.
const mostPerformant = (fns, iterations = 10000) => {
   const times = fns.map(fn => {
     const before = performance.now();
     for (let i = 0; i < iterations; i++) fn();
@@ -197,13 +197,13 @@ Logs: {
     [1, '2', 3, 4, 5, 6, 7, 8, 9, 10].every(el => typeof el === 'number');
   }
 ]); // 1
-
beginner
nthArg
Creates a function that gets the argument at index n. If n is negative, the nth argument from the end is returned.
Use Array.slice() to get the desired argument at index n.
const nthArg = n => (...args) => args.slice(n)[0];
+
nthArg
Creates a function that gets the argument at index n. If n is negative, the nth argument from the end is returned.
Use Array.slice() to get the desired argument at index n.
const nthArg = n => (...args) => args.slice(n)[0];
 
const third = nthArg(2);
 third(1, 2, 3); // 3
 third(1, 2); // undefined
 const last = nthArg(-1);
 last(1, 2, 3, 4, 5); // 5
-
intermediate
parseCookie
Parse an HTTP Cookie header string and return an object of all cookie name-value pairs.
Use String.split(';') to separate key-value pairs from each other. Use Array.map() and String.split('=') to separate keys from values in each pair. Use Array.reduce() and decodeURIComponent() to create an object with all key-value pairs.
const parseCookie = str =>
+
parseCookie
Parse an HTTP Cookie header string and return an object of all cookie name-value pairs.
Use String.split(';') to separate key-value pairs from each other. Use Array.map() and String.split('=') to separate keys from values in each pair. Use Array.reduce() and decodeURIComponent() to create an object with all key-value pairs.
const parseCookie = str =>
   str
     .split(';')
     .map(v => v.split('='))
@@ -212,7 +212,7 @@ Logs: {
       return acc;
     }, {});
 
parseCookie('foo=bar; equation=E%3Dmc%5E2'); // { foo: 'bar', equation: 'E=mc^2' }
-
advanced
prettyBytes
Converts a number in bytes to a human-readable string.
Use an array dictionary of units to be accessed based on the exponent. Use Number.toPrecision() to truncate the number to a certain number of digits. Return the prettified string by building it up, taking into account the supplied options and whether it is negative or not. Omit the second argument, precision, to use a default precision of 3 digits. Omit the third argument, addSpace, to add space between the number and unit by default.
const prettyBytes = (num, precision = 3, addSpace = true) => {
+
prettyBytes
Converts a number in bytes to a human-readable string.
Use an array dictionary of units to be accessed based on the exponent. Use Number.toPrecision() to truncate the number to a certain number of digits. Return the prettified string by building it up, taking into account the supplied options and whether it is negative or not. Omit the second argument, precision, to use a default precision of 3 digits. Omit the third argument, addSpace, to add space between the number and unit by default.
const prettyBytes = (num, precision = 3, addSpace = true) => {
   const UNITS = ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
   if (Math.abs(num) < 1) return num + (addSpace ? ' ' : '') + UNITS[0];
   const exponent = Math.min(Math.floor(Math.log10(num < 0 ? -num : num) / 3), UNITS.length - 1);
@@ -222,32 +222,32 @@ Logs: {
 
prettyBytes(1000); // "1 KB"
 prettyBytes(-27145424323.5821, 5); // "-27.145 GB"
 prettyBytes(123456789, 3, false); // "123MB"
-
beginner
randomHexColorCode
Generates a random hexadecimal color code.
Use Math.random to generate a random 24-bit(6x4bits) hexadecimal number. Use bit shifting and then convert it to an hexadecimal String using toString(16).
const randomHexColorCode = () => {
+
randomHexColorCode
Generates a random hexadecimal color code.
Use Math.random to generate a random 24-bit(6x4bits) hexadecimal number. Use bit shifting and then convert it to an hexadecimal String using toString(16).
const randomHexColorCode = () => {
   let n = (Math.random() * 0xfffff * 1000000).toString(16);
   return '#' + n.slice(0, 6);
 };
 
randomHexColorCode(); // "#e34155"
-
intermediate
RGBToHex
Converts the values of RGB components to a color code.
Convert given RGB parameters to hexadecimal string using bitwise left-shift operator (<<) and toString(16), then String.padStart(6,'0') to get a 6-digit hexadecimal value.
const RGBToHex = (r, g, b) => ((r << 16) + (g << 8) + b).toString(16).padStart(6, '0');
+
RGBToHex
Converts the values of RGB components to a color code.
Convert given RGB parameters to hexadecimal string using bitwise left-shift operator (<<) and toString(16), then String.padStart(6,'0') to get a 6-digit hexadecimal value.
const RGBToHex = (r, g, b) => ((r << 16) + (g << 8) + b).toString(16).padStart(6, '0');
 
RGBToHex(255, 165, 1); // 'ffa501'
-
intermediate
serializeCookie
Serialize a cookie name-value pair into a Set-Cookie header string.
Use template literals and encodeURIComponent() to create the appropriate string.
const serializeCookie = (name, val) => `${encodeURIComponent(name)}=${encodeURIComponent(val)}`;
+
serializeCookie
Serialize a cookie name-value pair into a Set-Cookie header string.
Use template literals and encodeURIComponent() to create the appropriate string.
const serializeCookie = (name, val) => `${encodeURIComponent(name)}=${encodeURIComponent(val)}`;
 
serializeCookie('foo', 'bar'); // 'foo=bar'
-
beginner
timeTaken
Measures the time taken by a function to execute.
Use console.time() and console.timeEnd() to measure the difference between the start and end times to determine how long the callback took to execute.
const timeTaken = callback => {
+
timeTaken
Measures the time taken by a function to execute.
Use console.time() and console.timeEnd() to measure the difference between the start and end times to determine how long the callback took to execute.
const timeTaken = callback => {
   console.time('timeTaken');
   const r = callback();
   console.timeEnd('timeTaken');
   return r;
 };
 
timeTaken(() => Math.pow(2, 10)); // 1024, (logged): timeTaken: 0.02099609375ms
-
intermediate
toCurrency
Take a number and return specified currency formatting.
Use Intl.NumberFormat to enable country / currency sensitive formatting.
const toCurrency = (n, curr, LanguageFormat = undefined) =>
+
toCurrency
Take a number and return specified currency formatting.
Use Intl.NumberFormat to enable country / currency sensitive formatting.
const toCurrency = (n, curr, LanguageFormat = undefined) =>
   Intl.NumberFormat(LanguageFormat, { style: 'currency', currency: curr }).format(n);
 
toCurrency(123456.789, 'EUR'); // €123,456.79  | currency: Euro | currencyLangFormat: Local
 toCurrency(123456.789, 'USD', 'en-us'); // $123,456.79  | currency: US Dollar | currencyLangFormat: English (United States)
 toCurrency(123456.789, 'USD', 'fa'); // ۱۲۳٬۴۵۶٫۷۹ ؜$ | currency: US Dollar | currencyLangFormat: Farsi
 toCurrency(322342436423.2435, 'JPY'); // ¥322,342,436,423 | currency: Japanese Yen | currencyLangFormat: Local
 toCurrency(322342436423.2435, 'JPY', 'fi'); // 322 342 436 423 ¥ | currency: Japanese Yen | currencyLangFormat: Finnish
-
beginner
toDecimalMark
Use toLocaleString() to convert a float-point arithmetic to the Decimal mark form. It makes a comma separated string from a number.
const toDecimalMark = num => num.toLocaleString('en-US');
+
toDecimalMark
Use toLocaleString() to convert a float-point arithmetic to the Decimal mark form. It makes a comma separated string from a number.
const toDecimalMark = num => num.toLocaleString('en-US');
 
toDecimalMark(12305030388.9087); // "12,305,030,388.909"
-
intermediate
toOrdinalSuffix
Adds an ordinal suffix to a number.
Use the modulo operator (%) to find values of single and tens digits. Find which ordinal pattern digits match. If digit is found in teens pattern, use teens ordinal.
const toOrdinalSuffix = num => {
+
toOrdinalSuffix
Adds an ordinal suffix to a number.
Use the modulo operator (%) to find values of single and tens digits. Find which ordinal pattern digits match. If digit is found in teens pattern, use teens ordinal.
const toOrdinalSuffix = num => {
   const int = parseInt(num),
     digits = [int % 10, int % 100],
     ordinals = ['st', 'nd', 'rd', 'th'],
@@ -258,12 +258,12 @@ Logs: {
     : int + ordinals[3];
 };
 
toOrdinalSuffix('123'); // "123rd"
-
intermediate
validateNumber
Returns true if the given value is a number, false otherwise.
Use !isNaN() in combination with parseFloat() to check if the argument is a number. Use isFinite() to check if the number is finite. Use Number() to check if the coercion holds.
const validateNumber = n => !isNaN(parseFloat(n)) && isFinite(n) && Number(n) == n;
+
validateNumber
Returns true if the given value is a number, false otherwise.
Use !isNaN() in combination with parseFloat() to check if the argument is a number. Use isFinite() to check if the number is finite. Use Number() to check if the coercion holds.
const validateNumber = n => !isNaN(parseFloat(n)) && isFinite(n) && Number(n) == n;
 
validateNumber('10'); // true
-
intermediate
yesNo
Returns true if the string is y/yes or false if the string is n/no.
Use RegExp.test() to check if the string evaluates to y/yes or n/no. Omit the second argument, def to set the default answer as no.
const yesNo = (val, def = false) =>
+
yesNo
Returns true if the string is y/yes or false if the string is n/no.
Use RegExp.test() to check if the string evaluates to y/yes or n/no. Omit the second argument, def to set the default answer as no.
const yesNo = (val, def = false) =>
   /^(y|yes)$/i.test(val) ? true : /^(n|no)$/i.test(val) ? false : def;
 
yesNo('Y'); // true
 yesNo('yes'); // true
 yesNo('No'); // false
 yesNo('Foo', true); // true
-

\ No newline at end of file
+
\ No newline at end of file diff --git a/scripts/web.js b/scripts/web.js index 67bac1f57..4c46911c1 100644 --- a/scripts/web.js +++ b/scripts/web.js @@ -196,7 +196,7 @@ try { for (let taggedSnippet of Object.entries(tagDbData).filter(v => v[1][0] === tag)) localOutput += '
' + - `
${taggedSnippet[1].includes('advanced') ? 'advanced' : taggedSnippet[1].includes('beginner') ? 'beginner' : 'intermediate'}
` + + `
` + md .render(`\n${snippets[taggedSnippet[0] + '.md']}`) .replace( @@ -209,7 +209,7 @@ try { ) .replace( /
/m,
-            '
'
+            '
'
           )
           .replace(
             /
([^\0]*?)<\/code><\/pre>/gm,
@@ -387,7 +387,7 @@ try {
         )
         .replace(
           /
/m,
-          '
'
+          '
'
         )
         .replace(
           /
([^\0]*?)<\/code><\/pre>/gm,
diff --git a/snippet_data/snippetAnalytics.json b/snippet_data/snippetAnalytics.json
index e600db798..60dec5070 100644
--- a/snippet_data/snippetAnalytics.json
+++ b/snippet_data/snippetAnalytics.json
@@ -15,6 +15,21 @@
         "hash": "8a036b5ffee127e5456d59e36f3c9abb24f1692f6a398b61c20ebacaae8380e4"
       }
     },
+    {
+      "id": "allEqual",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 57,
+        "tokenCount": 21,
+        "functionCount": 1,
+        "operatorCount": 4,
+        "keywordCount": 1,
+        "distinctFunctionCount": 1
+      },
+      "meta": {
+        "hash": "aa5122e8272d9ef81a634e960da9b0ddbe6d670cb3e801d7ffd17ba36cd1630a"
+      }
+    },
     {
       "id": "any",
       "type": "snippetAnalysis",
@@ -45,6 +60,21 @@
         "hash": "4fa8b87ac30ec67afe40c80101a702986dd1e5cab3cd8b9653f1b7c8cbac7540"
       }
     },
+    {
+      "id": "arrayToCSV",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 109,
+        "tokenCount": 41,
+        "functionCount": 4,
+        "operatorCount": 5,
+        "keywordCount": 1,
+        "distinctFunctionCount": 2
+      },
+      "meta": {
+        "hash": "47f27df615f87cf59e53ae3a618249f8413dd9d9c8939296a8b8f3785697de3d"
+      }
+    },
     {
       "id": "arrayToHtmlList",
       "type": "snippetAnalysis",
@@ -109,15 +139,15 @@
       "id": "average",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 88,
-        "tokenCount": 40,
+        "codeLength": 83,
+        "tokenCount": 36,
         "functionCount": 1,
-        "operatorCount": 7,
+        "operatorCount": 6,
         "keywordCount": 1,
         "distinctFunctionCount": 1
       },
       "meta": {
-        "hash": "684bb67aac10990814a49d1d1878d98ec6d2161bd71f769a128e3195f9aeb632"
+        "hash": "992835ed744ef767f4cdf46f9881cca57a73695e2a8637a383490bf44369d31b"
       }
     },
     {
@@ -169,15 +199,15 @@
       "id": "bind",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 115,
-        "tokenCount": 43,
-        "functionCount": 2,
-        "operatorCount": 4,
-        "keywordCount": 3,
-        "distinctFunctionCount": 2
+        "codeLength": 100,
+        "tokenCount": 41,
+        "functionCount": 1,
+        "operatorCount": 7,
+        "keywordCount": 1,
+        "distinctFunctionCount": 1
       },
       "meta": {
-        "hash": "e9d5d908df4751e5765b1e7d5a5f883261bdfad521b01023a81d616cac3b3cc1"
+        "hash": "4909c73d0435a32df36abef06a58c21362ed3991aedc95421516a5d0ea83264a"
       }
     },
     {
@@ -199,15 +229,15 @@
       "id": "bindKey",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 127,
-        "tokenCount": 46,
-        "functionCount": 2,
-        "operatorCount": 4,
-        "keywordCount": 3,
-        "distinctFunctionCount": 2
+        "codeLength": 114,
+        "tokenCount": 44,
+        "functionCount": 1,
+        "operatorCount": 7,
+        "keywordCount": 1,
+        "distinctFunctionCount": 1
       },
       "meta": {
-        "hash": "561c7894f3ca7df0b3874ea749320b7d97eb3118c07c2636f4c4215377697927"
+        "hash": "cfbb9759a71b09d9351a02f39f828578290e389aeb5390ce760957ee43be0297"
       }
     },
     {
@@ -600,6 +630,36 @@
         "hash": "e952a30a27c1465ea9ac465d4b7de3f9dda6e58279c176bc7c0e98fb6d99f1fc"
       }
     },
+    {
+      "id": "CSVToArray",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 180,
+        "tokenCount": 60,
+        "functionCount": 5,
+        "operatorCount": 7,
+        "keywordCount": 1,
+        "distinctFunctionCount": 4
+      },
+      "meta": {
+        "hash": "323a85ce03cc446dcfc3dfd8a89b4501b217b0e846fa73b99a6c3e2ee51a1caf"
+      }
+    },
+    {
+      "id": "CSVToJSON",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 341,
+        "tokenCount": 126,
+        "functionCount": 9,
+        "operatorCount": 9,
+        "keywordCount": 5,
+        "distinctFunctionCount": 5
+      },
+      "meta": {
+        "hash": "de42726725b56d870fa0a7b16dc327589bbeba5a6d821d5f43d09b8a478a139a"
+      }
+    },
     {
       "id": "currentURL",
       "type": "snippetAnalysis",
@@ -690,6 +750,21 @@
         "hash": "31714831376eeddd863a295af778632f584468745fbeb4e9a6f62b5275ea3562"
       }
     },
+    {
+      "id": "deepFreeze",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 188,
+        "tokenCount": 64,
+        "functionCount": 5,
+        "operatorCount": 7,
+        "keywordCount": 3,
+        "distinctFunctionCount": 5
+      },
+      "meta": {
+        "hash": "24b3dd66c4b69577d70917ba4f0c119a7ad21497d18704b7150c3693673b5e53"
+      }
+    },
     {
       "id": "defaults",
       "type": "snippetAnalysis",
@@ -810,6 +885,21 @@
         "hash": "e80b6619b9690e2a5d5cfd9d5fbe77fc25b6698e580e4b36e2c3c5fc54e3e572"
       }
     },
+    {
+      "id": "dig",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 236,
+        "tokenCount": 79,
+        "functionCount": 3,
+        "operatorCount": 6,
+        "keywordCount": 7,
+        "distinctFunctionCount": 3
+      },
+      "meta": {
+        "hash": "0f53175b7bf367b55e612ccca6061c8e2a3db68af00950af2fda92746055cc05"
+      }
+    },
     {
       "id": "digitize",
       "type": "snippetAnalysis",
@@ -934,22 +1024,22 @@
       "id": "elo",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 613,
-        "tokenCount": 258,
+        "codeLength": 580,
+        "tokenCount": 248,
         "functionCount": 4,
-        "operatorCount": 31,
-        "keywordCount": 12,
+        "operatorCount": 30,
+        "keywordCount": 11,
         "distinctFunctionCount": 3
       },
       "meta": {
-        "hash": "c345e1ea4c044879d78a3f141d76dc90b311d7a78818d3a16e4f7335a9d0c779"
+        "hash": "3fc1fe2b64b13a3064c547933e759c0782bd43f357056a467d0ce2cc7e9a38e3"
       }
     },
     {
       "id": "equals",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 489,
+        "codeLength": 490,
         "tokenCount": 197,
         "functionCount": 6,
         "operatorCount": 24,
@@ -957,7 +1047,7 @@
         "distinctFunctionCount": 4
       },
       "meta": {
-        "hash": "ebb0ab118f56fb88df192400decf89e9cb27074a4e86eccf0b145f373082701e"
+        "hash": "7682a58d7745903fc19aa4341b8594d85714d563cfda1b44779bc0663338c3cf"
       }
     },
     {
@@ -1065,6 +1155,21 @@
         "hash": "8f319457b4350e041ba31cd4b4d02135013d8ea6716d0a4d00cf1b1bfd214ffa"
       }
     },
+    {
+      "id": "filterNonUniqueBy",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 113,
+        "tokenCount": 57,
+        "functionCount": 3,
+        "operatorCount": 6,
+        "keywordCount": 1,
+        "distinctFunctionCount": 3
+      },
+      "meta": {
+        "hash": "39812240e9f09488915843a8ecb6373908513a7a469c00b120779ca462c651c5"
+      }
+    },
     {
       "id": "findKey",
       "type": "snippetAnalysis",
@@ -1189,15 +1294,15 @@
       "id": "formatDuration",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 427,
-        "tokenCount": 182,
+        "codeLength": 421,
+        "tokenCount": 154,
         "functionCount": 9,
-        "operatorCount": 22,
+        "operatorCount": 17,
         "keywordCount": 4,
         "distinctFunctionCount": 5
       },
       "meta": {
-        "hash": "79051bd95886abf6856585481e3c9cb0685e197bad764a56eb583bd3421f3449"
+        "hash": "fcaccacf92e1a1e5f8610cf78b840a6b897fc5e6cadb54d7a32efadb71b99f80"
       }
     },
     {
@@ -1549,15 +1654,15 @@
       "id": "hide",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 73,
-        "tokenCount": 35,
+        "codeLength": 65,
+        "tokenCount": 26,
         "functionCount": 1,
-        "operatorCount": 6,
+        "operatorCount": 4,
         "keywordCount": 1,
         "distinctFunctionCount": 1
       },
       "meta": {
-        "hash": "936ca95ab4a3a012580a45574f77cb8f8c2b70d60e8506627bf4eb2ef8743fa2"
+        "hash": "8b7b70809f93fd9392315a5c63aa4cbbf9b45eb1165a7d44db314186d407816b"
       }
     },
     {
@@ -1624,15 +1729,15 @@
       "id": "indexOfAll",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 134,
-        "tokenCount": 53,
-        "functionCount": 2,
+        "codeLength": 98,
+        "tokenCount": 49,
+        "functionCount": 1,
         "operatorCount": 6,
-        "keywordCount": 3,
-        "distinctFunctionCount": 2
+        "keywordCount": 1,
+        "distinctFunctionCount": 1
       },
       "meta": {
-        "hash": "e2842e376c747f02bce3cddbcbbc55ca9ed8a06701b2e0f4fb4215b97951ff13"
+        "hash": "643cb7b5df16c9da268e21b65b4cf73bb572e7b93a5859d09bb3bc949665f65b"
       }
     },
     {
@@ -1669,15 +1774,15 @@
       "id": "initializeArrayWithRange",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 157,
-        "tokenCount": 65,
-        "functionCount": 2,
+        "codeLength": 153,
+        "tokenCount": 62,
+        "functionCount": 1,
         "operatorCount": 10,
         "keywordCount": 2,
-        "distinctFunctionCount": 2
+        "distinctFunctionCount": 1
       },
       "meta": {
-        "hash": "dcd2209a400e3bc7df0157df52faf794c628b80c625b9f5d9f15625f269890b0"
+        "hash": "f2cb7d6d0d34691affe17f7c06ee5c45944bd9515298560a18543f0798b4fe13"
       }
     },
     {
@@ -1729,15 +1834,15 @@
       "id": "inRange",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 173,
-        "tokenCount": 76,
+        "codeLength": 169,
+        "tokenCount": 74,
         "functionCount": 0,
-        "operatorCount": 15,
+        "operatorCount": 14,
         "keywordCount": 5,
         "distinctFunctionCount": 0
       },
       "meta": {
-        "hash": "fe2b9483c3a173e426aba3e834d6b97008b840ea40e54c8eabb06e1da9832872"
+        "hash": "cb00d1c23e02506fc968515ce8c18dcec8837d447cd47a99f73777574308fb49"
       }
     },
     {
@@ -1789,15 +1894,15 @@
       "id": "intersectionBy",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 119,
-        "tokenCount": 62,
-        "functionCount": 5,
-        "operatorCount": 5,
+        "codeLength": 111,
+        "tokenCount": 56,
+        "functionCount": 4,
+        "operatorCount": 4,
         "keywordCount": 4,
         "distinctFunctionCount": 4
       },
       "meta": {
-        "hash": "4df9daee1b38b51d92741ea763fdfb42e85331c1cb747ec413c45543243f1f48"
+        "hash": "78c90426a81372be83af6ef2bdee0147263361673ab99fa2315ead2720d991b8"
       }
     },
     {
@@ -1879,15 +1984,15 @@
       "id": "isArrayLike",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 104,
-        "tokenCount": 44,
+        "codeLength": 85,
+        "tokenCount": 26,
         "functionCount": 0,
-        "operatorCount": 3,
-        "keywordCount": 5,
+        "operatorCount": 5,
+        "keywordCount": 3,
         "distinctFunctionCount": 0
       },
       "meta": {
-        "hash": "0d30400ab43a3e2706c3684495c9ae80361b50ca0606c7bbd4f96ca423c89c18"
+        "hash": "00b43a2b430d5d9205046ad6fbf7442f0d4507895c82545753253b5b5f97fa3a"
       }
     },
     {
@@ -2265,6 +2370,21 @@
         "hash": "05c13ad111a5815d05ba0d2ca0bb17a7ab7e02fc3b33f0e5e049acc25fc2cbb4"
       }
     },
+    {
+      "id": "JSONtoCSV",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 263,
+        "tokenCount": 62,
+        "functionCount": 4,
+        "operatorCount": 6,
+        "keywordCount": 1,
+        "distinctFunctionCount": 3
+      },
+      "meta": {
+        "hash": "65457b943f03456c28e947f21177ffd0c9d8a00eb37aab7f7f76cb666f8c0acc"
+      }
+    },
     {
       "id": "JSONToFile",
       "type": "snippetAnalysis",
@@ -2314,15 +2434,15 @@
       "id": "longestItem",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 82,
-        "tokenCount": 39,
+        "codeLength": 103,
+        "tokenCount": 49,
         "functionCount": 1,
-        "operatorCount": 6,
+        "operatorCount": 7,
         "keywordCount": 1,
         "distinctFunctionCount": 1
       },
       "meta": {
-        "hash": "dae3111792b57ac2ac698374e2eb0e568e8910041940fd0240053387a8dd72e3"
+        "hash": "cb9de7acf3a94ee67a24d7d5926944124ad0bd3459126c2f740f868fbffc655b"
       }
     },
     {
@@ -2385,6 +2505,21 @@
         "hash": "c7f0f9b6b22590a17c41057c56ea5cf14e74dfbbd4fb7e4bc5c08db3760ef76d"
       }
     },
+    {
+      "id": "mapString",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 100,
+        "tokenCount": 47,
+        "functionCount": 4,
+        "operatorCount": 3,
+        "keywordCount": 1,
+        "distinctFunctionCount": 4
+      },
+      "meta": {
+        "hash": "828991c05b86fc84f46155e1452cada09bd3cb64f734533af7bf4cabe3077aab"
+      }
+    },
     {
       "id": "mapValues",
       "type": "snippetAnalysis",
@@ -2599,15 +2734,15 @@
       "id": "nodeListToArray",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 73,
-        "tokenCount": 18,
-        "functionCount": 1,
-        "operatorCount": 2,
+        "codeLength": 50,
+        "tokenCount": 13,
+        "functionCount": 0,
+        "operatorCount": 3,
         "keywordCount": 1,
-        "distinctFunctionCount": 1
+        "distinctFunctionCount": 0
       },
       "meta": {
-        "hash": "c11457d105eebd90dbaabc970dd03a4d3868b740e0a52f4d813957bae7324740"
+        "hash": "50e0b97be1cc2256f34991c379bae0bba8c99db160dcd5842112752074de92ec"
       }
     },
     {
@@ -2644,15 +2779,15 @@
       "id": "nthElement",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 83,
-        "tokenCount": 48,
+        "codeLength": 86,
+        "tokenCount": 49,
         "functionCount": 2,
-        "operatorCount": 6,
+        "operatorCount": 7,
         "keywordCount": 1,
         "distinctFunctionCount": 1
       },
       "meta": {
-        "hash": "8d86827300570ea124917756dd740f33f5d12b59487e889ebcad2e1172bf1993"
+        "hash": "94f23b748d064fc620e820b9f858e0b191c68be84c9af6d8740fe48618005870"
       }
     },
     {
@@ -3274,15 +3409,15 @@
       "id": "rearg",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 188,
-        "tokenCount": 76,
-        "functionCount": 3,
-        "operatorCount": 7,
-        "keywordCount": 2,
-        "distinctFunctionCount": 3
+        "codeLength": 77,
+        "tokenCount": 37,
+        "functionCount": 2,
+        "operatorCount": 6,
+        "keywordCount": 1,
+        "distinctFunctionCount": 2
       },
       "meta": {
-        "hash": "4117e1a4abc2008657ac12d2ca949d05dceb9f3c303feb1828605b6010441fe5"
+        "hash": "ed859f031cdc8a778bcec23817f79dab36f7607424fedda33d8d997172404de1"
       }
     },
     {
@@ -3457,7 +3592,7 @@
         "codeLength": 92,
         "tokenCount": 31,
         "functionCount": 1,
-        "operatorCount": 4,
+        "operatorCount": 3,
         "keywordCount": 1,
         "distinctFunctionCount": 1
       },
@@ -3912,7 +4047,7 @@
         "distinctFunctionCount": 2
       },
       "meta": {
-        "hash": "a353d35fc5fb8ec4ebbf0856079a823a598a5023ca908a7b1ddca55b4b3b60fe"
+        "hash": "476d7ee29bd0750a4c0f428c7e17a612ea50ee002eb865733f8d312b79a0c5a3"
       }
     },
     {
@@ -4332,7 +4467,7 @@
         "distinctFunctionCount": 9
       },
       "meta": {
-        "hash": "30a3f0e6f8386104c06eedd1dc1ab44e3c3c4c2a150b920b4093ae4234ea03f5"
+        "hash": "aee8b10b831e676337688628f9204cea2019a008c30005f0760432d86498fc3f"
       }
     },
     {
@@ -4410,6 +4545,51 @@
         "hash": "e45f1af52564b0b1d91ce8bce53fe98ce888f3c943e1c1828682893393540256"
       }
     },
+    {
+      "id": "uniqueElementsBy",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 137,
+        "tokenCount": 65,
+        "functionCount": 4,
+        "operatorCount": 5,
+        "keywordCount": 3,
+        "distinctFunctionCount": 4
+      },
+      "meta": {
+        "hash": "8640aeb79ced5defcc89555176a88acd66bca74f4359dc41388b5687f2050015"
+      }
+    },
+    {
+      "id": "uniqueElementsByRight",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 147,
+        "tokenCount": 65,
+        "functionCount": 4,
+        "operatorCount": 5,
+        "keywordCount": 3,
+        "distinctFunctionCount": 4
+      },
+      "meta": {
+        "hash": "853887ad00b7c39a719c5b7e16dd3464a85f08da43d9d1bd1e7b7ebeaa897c95"
+      }
+    },
+    {
+      "id": "uniqueSymmetricDifference",
+      "type": "snippetAnalysis",
+      "attributes": {
+        "codeLength": 131,
+        "tokenCount": 61,
+        "functionCount": 4,
+        "operatorCount": 9,
+        "keywordCount": 2,
+        "distinctFunctionCount": 2
+      },
+      "meta": {
+        "hash": "58712a3aee2c952a18d9f0d2f21d0002ac720d0d0f8fe082d02f891e3912bf1d"
+      }
+    },
     {
       "id": "untildify",
       "type": "snippetAnalysis",
diff --git a/snippet_data/snippetArchiveAnalytics.json b/snippet_data/snippetArchiveAnalytics.json
index 958c041dd..4e76a1239 100644
--- a/snippet_data/snippetArchiveAnalytics.json
+++ b/snippet_data/snippetArchiveAnalytics.json
@@ -199,7 +199,7 @@
       "id": "levenshteinDistance",
       "type": "snippetAnalysis",
       "attributes": {
-        "codeLength": 707,
+        "codeLength": 709,
         "tokenCount": 3,
         "functionCount": 0,
         "operatorCount": 0,
@@ -207,7 +207,7 @@
         "distinctFunctionCount": 0
       },
       "meta": {
-        "hash": "78b4ba08e503af63ca7811cd174218c55db9e0f726439a8c429dedeff0731d80"
+        "hash": "170ef4eafeb5ac639c721f1a8e02d309e1ad62941c613ce60462fa72274f4c25"
       }
     },
     {
@@ -237,7 +237,7 @@
         "distinctFunctionCount": 3
       },
       "meta": {
-        "hash": "f654dce947e6e48d66ba5d29452c35c6031e59add0a0124ffed1239317c40ebe"
+        "hash": "878970d0bdefe60f7f61db64b85bbb36b6869e2875a2c278fb269b8cff3b42b4"
       }
     },
     {
diff --git a/static-parts/about.html b/static-parts/about.html
index 5cdc41d1d..bc3d84ba0 100644
--- a/static-parts/about.html
+++ b/static-parts/about.html
@@ -115,7 +115,7 @@
             license.
Logos made by Angelos Chalaris and ribbon made by Tim Holman are licensed under the MIT
             license.
Sponsored by DigitalOcean

+              width="20px" height="20px" alt="DigitalOcean">DigitalOcean

           

           
About    Contributing    Archive    Glossary

diff --git a/static-parts/archived-page-end.html b/static-parts/archived-page-end.html
index ee6ad478b..4c8d4a667 100644
--- a/static-parts/archived-page-end.html
+++ b/static-parts/archived-page-end.html
@@ -5,7 +5,7 @@
       license.
Logos made by Angelos Chalaris and ribbon made by Tim Holman are licensed under the MIT
       license.
Sponsored by DigitalOcean.

+        width="20px" height="20px" alt="DigitalOcean">DigitalOcean.

     

     
About    Contributing    Archive    Glossary

diff --git a/static-parts/beginner-page-end.html b/static-parts/beginner-page-end.html
index 63caf6452..e17fd2658 100644
--- a/static-parts/beginner-page-end.html
+++ b/static-parts/beginner-page-end.html
@@ -2,6 +2,6 @@
     
     
     

-    
+    
   
 
diff --git a/static-parts/contributing.html b/static-parts/contributing.html
index a3b47913b..ba8c610e6 100644
--- a/static-parts/contributing.html
+++ b/static-parts/contributing.html
@@ -66,7 +66,7 @@
             license.
Logos made by Angelos Chalaris and ribbon made by Tim Holman are licensed under the MIT
             license.
Sponsored by DigitalOcean.

+              width="20px" height="20px" alt="DigitalOcean">DigitalOcean.

           

           
About    Contributing    Archive    Glossary

diff --git a/static-parts/glossary-page-end.html b/static-parts/glossary-page-end.html
index ee6ad478b..4c8d4a667 100644
--- a/static-parts/glossary-page-end.html
+++ b/static-parts/glossary-page-end.html
@@ -5,7 +5,7 @@
       license.
Logos made by Angelos Chalaris and ribbon made by Tim Holman are licensed under the MIT
       license.
Sponsored by DigitalOcean.

+        width="20px" height="20px" alt="DigitalOcean">DigitalOcean.

     

     
About    Contributing    Archive    Glossary

diff --git a/static-parts/page-end.html b/static-parts/page-end.html
index a3e5d1750..1a368584e 100644
--- a/static-parts/page-end.html
+++ b/static-parts/page-end.html
@@ -2,7 +2,7 @@