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 );
+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 ]
const map = call.bind(null, 'map')
@@ -251,7 +251,7 @@ Promise.resolve( [ 1, 2, 3 ] ).then( map( x => 2 * x ) ).then( console.log )
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 collectInto = fn => (...args) => fn(args);
const Pall = collectInto( Promise.all.bind(Promise) )
let p1 = Promise.resolve(1)
@@ -313,8 +313,8 @@ arrayMax([1,2,4]) // 4
Use Array.reduce() and the gcd formula (uses recursion) to calculate the greatest common denominator of an array of numbers.
const arrayGcd = arr => {
const gcd = (x, y) => !y ? x : gcd(y, x % y);
- return arr.reduce((a,b) => gcd(a,b));
-}
+ return arr.reduce((a, b) => gcd(a, b));
+};
arrayGcd([1,2,3,4,5]) // 1
arrayGcd([4,8,12]) // 4
@@ -324,9 +324,9 @@ arrayGcd([4,8,12]) // 4
Use Array.reduce() and the lcm formula (uses recursion) to calculate the lowest common multiple of an array of numbers.
const arrayLcm = 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));
-}
+ const lcm = (x, y) => (x * y) / gcd(x, y);
+ return arr.reduce((a, b) => lcm(a, b));
+};
arrayLcm([1,2,3,4,5]) // 60
arrayLcm([4,8,12]) // 24
@@ -388,7 +388,7 @@ Recursively flatten each element that is an array.
Filters out all values from an array for which the comparator function does not return true.
Use Array.filter() and Array.find() to find the appropriate values.
const differenceWith = (arr, val, comp) => arr.filter(a => !val.find(b => comp(a, b)))
+const differenceWith = (arr, val, comp) => arr.filter(a => !val.find(b => comp(a, b)));
differenceWith([1, 1.2, 1.5, 3], [1.9, 3], (a,b) => Math.round(a) == Math.round(b)) // [1, 1.2]
@@ -436,7 +436,7 @@ dropRight([1,2,3], 42) // []
Flattens an array.
Use a new array and concatenate it with the spread input array causing a shallow denesting of any contained arrays.
-const flatten = arr => [ ].concat( ...arr );
+const flatten = arr => [ ].concat(...arr);
flatten([1,[2],3,4]) // [1,2,3,4]
@@ -450,7 +450,7 @@ Omit the second element, depth to flatten only to a depth of
depth != 1 ? arr.reduce((a, v) => a.concat(Array.isArray(v) ? flattenDepth(v, depth - 1) : v), [])
: arr.reduce((a, v) => a.concat(v), []);
flatten([1,[2],3,4]) // [1,2,3,4]
+flattenDepth([1,[2],3,4]) // [1,2,3,4]
Groups the elements of an array based on the given function.
@@ -520,7 +520,7 @@ You can omitvalue to use a default value of 0.
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), {}) )) ( );
+ (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 }
@@ -530,7 +530,7 @@ squareIt([1,2,3]) // { 1: 1, 2: 4, 3: 9 }
Use Array.slice() to get an array containing the nth element at the first place.
If the index is out of bounds, return [].
Omit the second argument, n, to get the first element of the array.
-const nthElement = (arr, n=0) => (n>0? arr.slice(n,n+1) : arr.slice(n))[0];
+const nthElement = (arr, n = 0) => (n > 0 ? arr.slice(n, n + 1) : arr.slice(n))[0];
nthElement(['a','b','c'],1) // 'b'
nthElement(['a','b','b'],-3) // 'a'
@@ -571,11 +571,11 @@ 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)
- .filter((v, i) => !pullArr.includes(i))
+ .filter((v, i) => !pullArr.includes(i));
arr.length = 0;
pulled.forEach(v => arr.push(v));
return removed;
-}
+};
let myArray = ['a', 'b', 'c', 'd'];
let pulled = pullAtIndex(myArray, [1, 3]);
@@ -595,7 +595,7 @@ Use Array.push() to keep track of pulled values
arr.length = 0;
mutateTo.forEach(v => arr.push(v));
return removed;
-}
+};
let myArray = ['a', 'b', 'c', 'd'];
let pulled = pullAtValue(myArray, ['b', 'd']);
@@ -651,7 +651,7 @@ console.log(foo) // [1,2,3]
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]
@@ -702,9 +702,9 @@ If lengths of the argument-arrays vary, undefined is used where no
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]);
- })
-}
+ return Array.from({length: arrays.length}, (_, k) => arrays[k][i]);
+ });
+};
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]]
@@ -712,7 +712,7 @@ zip(['a'], [1, 2], [true, false]); // [['a', 1, true], [undefined, 2, false]]
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 ), {} )
+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}
@@ -721,7 +721,7 @@ zipObject(['a','b'], [1,2,3]) // {a: 1, b: 2}
arrayToHtmlList
Converts the given array elements into <li> tags and appends them to the list of the given id.
Use Array.map() and document.querySelector() to create a list of html tags.
-const arrayToHtmlList = (arr, listID) => arr.map(item => document.querySelector("#"+listID).innerHTML+=`<li>${item}</li>`);
+const arrayToHtmlList = (arr, listID) => arr.map(item => document.querySelector('#' + listID).innerHTML += `<li>${item}</li>`);
arrayToHtmlList(['item 1', 'item 2'],'myListID')
@@ -731,7 +731,7 @@ zipObject(['a','b'], [1,2,3]) // {a: 1, b: 2}
const bottomVisible = () =>
document.documentElement.clientHeight + window.scrollY >= (document.documentElement.scrollHeight || document.documentElement.clientHeight);
-// bottomVisible() // true
+bottomVisible() // true
currentURL
Returns the current URL.
@@ -743,7 +743,7 @@ zipObject(['a','b'], [1,2,3]) // {a: 1, b: 2}
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";
+const detectDeviceType = () => /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ? 'Mobile' : 'Desktop';
detectDeviceType() // "Mobile"
detectDeviceType() // "Desktop"
@@ -848,7 +848,8 @@ Throws an error if the passed time cannot be converted to a date.
Results in a string representation of tomorrow's date.
Use new Date() to get today's date, adding 86400000 of seconds to it(24 hours), using toISOString to convert Date object to string.
const tomorrow = () => new Date(new Date().getTime() + 86400000).toISOString().split('T')[0];
-// tomorrow() -> 2017-12-27 (if current date is 2017-12-26)
+
+tomorrow() // 2017-12-27 (if current date is 2017-12-26)
Function
chainAsync
@@ -941,7 +942,7 @@ negate(isOdd)(1) // false
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));
+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
@@ -959,7 +960,7 @@ collatz(5) // 16
Converts a number to an array of digits.
Convert the number to a string, using spread operators in ES6([...string]) build an array.
Use Array.map() and parseInt() to transform each value to an integer.
-const digitize = n => [...''+n].map(i => parseInt(i));
+const digitize = n => [...'' + n].map(i => parseInt(i));
differenceWith([1, 1.2, 1.5, 3], [1.9, 3], (a,b) => Math.round(a) == Math.round(b)) // [1, 1.2]
@@ -989,13 +990,13 @@ Use Array.reduce() to add values into the array, using the sum of t
const fibonacci = n =>
Array.from({ length: n}).reduce((acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i), []);
-factorial(6) // 720
+fibonacci(6) // 720
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));
+ Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
fibonacciCountUntilNum(10) // 7
@@ -1007,7 +1008,7 @@ 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), []);
-}
+};
fibonacciCountUntilNum(10) // 7
@@ -1033,10 +1034,10 @@ Count and return the number of 1s in the string, using match(
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][0];
- return (end == null) ? (n>=0 && n<start) : (n>=start && n<end);
-}
+const inRange = (n, start, end = null) => {
+ if (end && start > end) end = [start, start = end][0];
+ return (end == null) ? (n >= 0 && n < start) : (n >= start && n < end);
+};
inRange(3, 2, 5) // true
inRange(3, 4) // true
@@ -1047,7 +1048,7 @@ inrange(3, 2) // false
Checks if the given number is an Armstrong number or not.
Convert the given number into an array of digits. Use Math.pow() 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 + Math.pow( parseInt( d ), arr.length ), 0 ) == digits ? true : false )( ( digits+'' ).split( '' ) );
+ (arr => arr.reduce((a, d) => a + Math.pow(parseInt(d), arr.length), 0) == digits)((digits + '').split(''));
isArmstrongNumber(1634) // true
isArmstrongNumber(371) // true
@@ -1109,9 +1110,9 @@ median([0,10,-2,7]) // 3.5
Convert string toLowerCase() and use replace() to remove non-alphanumeric characters from it.
Then, split('') into individual characters, reverse(), join('') and compare to the original, unreversed string, after converting it tolowerCase().
const palindrome = str => {
- const s = str.toLowerCase().replace(/[\W_]/g,'');
+ const s = str.toLowerCase().replace(/[\W_]/g, '');
return s === s.split('').reverse().join('');
-}
+};
palindrome('taco cat') // true
@@ -1119,7 +1120,7 @@ Then, split('') into individual characters, reverse(),
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;
+ 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
@@ -1135,12 +1136,12 @@ Then, split('') into individual characters, reverse(),
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);
- numsTillSqroot.forEach(x => arr = arr.filter(y => ((y%x)!==0)||(y==x)));
+ 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);
+ numsTillSqroot.forEach(x => arr = arr.filter(y => ((y % x) !== 0) || (y == x)));
return arr;
-}
+};
primes(10) // [2,3,5,7]
@@ -1162,22 +1163,10 @@ Then, split('') into individual characters, reverse(),
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}`);
+const round = (n, decimals = 0) => Number(`${Math.round(`${n}e${decimals}`)}e-${decimals}`);
round(1.005, 2) // 1.01
-
sdbmHashAlgorithm
-This algorithm is a simple hash-algorithm that hashes it input string s into a whole number.
-Use 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) =>
- hashCode = currentVal.charCodeAt(0) + (hashCode << 6) + (hashCode << 16) - hashCode
- ,0)
-}
-// console.log(sdbm("name")) // -3521204949
-// console.log(sdbm("age")) // 808122783
-
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
@@ -1213,7 +1202,7 @@ Use window.speechSynthesis.speak() to play the message.
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(`${filename}.json`, JSON.stringify(obj, null, 2))
+const JSONToFile = (obj, filename) => fs.writeFile(`${filename}.json`, JSON.stringify(obj, null, 2));
JSONToFile({test: "is passed"}, 'testJsonFile') // writes the object to 'testJsonFile.json'
@@ -1235,14 +1224,6 @@ contents of test.txt :
let arr = readFileLines('test.txt')
console.log(arr) // ['line1', 'line2', 'line3']
-contents of test.txt :
- line1
- line2
- line3
- ___________________________
-let arr = readFileLines('test.txt')
-console.log(arr) // // ['line1', 'line2', 'line3']
-
Object
cleanObj
Removes any properties except the ones specified from a JSON object.
@@ -1383,9 +1364,9 @@ fromCamelCase('someJavascriptProperty', '_') // 'some_javascript_property'
repeatString
Repeats a string n times using String.repeat()
If no string is provided the default is "" and the default number of times is 2.
-const repeatString = (str="",num=2) => {
- return num >= 0 ? str.repeat(num) : str;
-}
+const repeatString = (str = '', num = 2) => {
+ return num >= 0 ? str.repeat(num) : str;
+};
repeatString("abc",3) // 'abcabcabc'
repeatString("abc") // 'abcabc'
@@ -1414,8 +1395,8 @@ For more detailed explanation of this Regex, toCamelCase("some_database_field_name") // 'someDatabaseFieldName'
toCamelCase("Some label that needs to be camelized") // 'someLabelThatNeedsToBeCamelized'
@@ -1476,7 +1457,7 @@ words("python, javaScript & coffee") // ["python", "
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(_))
+const coalesce = (...args) => args.find(_ => ![undefined, null].includes(_));
coalesce(null,undefined,"",NaN, "Waldo") // ""
@@ -1493,7 +1474,7 @@ customCoalesce(undefined, null, NaN, "", "Waldo") // "W
Use Array.map(), split() and Array.join() to join the mapped array for converting a 3-digit RGB notated hexadecimal color-code to the 6-digit form.
String.slice() is used to remove # from string start since it's added once.
const extendHex = shortHex =>
- '#' + shortHex.slice(shortHex.startsWith('#') ? 1 : 0).split('').map(x => x+x).join('')
+ '#' + shortHex.slice(shortHex.startsWith('#') ? 1 : 0).split('').map(x => x + x).join('');
extendHex('#03f') // '#0033ff'
extendHex('05a') // '#0055aa'
@@ -1573,14 +1554,14 @@ isString('10') // true
isSymbol('x') // false
isSymbol(Symbol('x')) // true
-
randomHexColor
+
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 randomHexColor = () => {
- let n = (Math.random() * 0xfffff | 0).toString(16);
- return '#' + (n.length !== 6
- ? (Math.random() * 0xf | 0).toString(16) + n : n);
-};
+const randomHexColorCode = () => {
+ let n = (Math.random() * 0xfffff | 0).toString(16);
+ return '#' + (n.length !== 6
+ ? (Math.random() * 0xf | 0).toString(16) + n : n);
+};
randomHexColorCode() // "#e34155"
randomHexColorCode() // "#fd73a6"
@@ -1593,6 +1574,19 @@ randomHexColorCode() // "#4144c6"
RGBToHex(255, 165, 1) // 'ffa501'
+
sbdm
+This algorithm is a simple hash-algorithm that hashes it input string s into a whole number.
+Use 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) =>
+ hashCode = currentVal.charCodeAt(0) + (hashCode << 6) + (hashCode << 16) - hashCode
+ ,0)
+}
+
+console.log(sdbm("name")) // -3521204949
+console.log(sdbm("age")) // 808122783
+
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.
@@ -1602,11 +1596,11 @@ randomHexColorCode() // "#4144c6"
};
timeTaken(() => Math.pow(2, 10)) // 1024
-(logged): timeTaken: 0.02099609375ms
+// (logged): timeTaken: 0.02099609375ms
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");
+const toDecimalMark = num => num.toLocaleString('en-US');
toDecimalMark(12305030388.9087) // "12,305,030,388.9087"