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 ]
+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')
Promise.resolve( [ 1, 2, 3 ] ).then( map( x => 2 * x ) ).then( console.log ) //[ 2, 4, 6 ]
-*/
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) )
+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)
-*/
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 => (...args) => fn(args.pop(), ...args);
-/*
-let a = {name: 'John Smith'}
+let a = {name: 'John Smith'}
let b = {}
const mergeFrom = flip(Object.assign)
let mergePerson = mergeFrom.bind(null, a)
mergePerson(b) // == b
b = {}
Object.assign(b, a) // == b
-*/
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 add5 = x => x + 5
const multiply = (x, y) => x * y
const multiplyAndAdd5 = pipeFunctions(multiply, add5)
-multiplyAndAdd5(5, 2) -> 15
-*/
+multiplyAndAdd5(5, 2) // 15
Converts an asynchronous function to return a promise.
@@ -298,18 +294,18 @@ Use the...rest operator to pass in all the parameters.
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
+
+const delay = promisify((d, cb) => setTimeout(cb, d))
+delay(2000).then(() => console.log('Hi!')) // // Promise resolves after 2s
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
-arrayMax([1,2,4]) // -> 4
-*/
+const arrayMax = spreadOver(Math.max)
+arrayMax([1,2,3]) // 3
+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));
-};
-// arrayGcd([1,2,3,4,5]) -> 1
-// arrayGcd([4,8,12]) -> 4
+ return arr.reduce((a,b) => gcd(a,b));
+}
+arrayGcd([1,2,3,4,5]) // 1
+arrayGcd([4,8,12]) // 4
Calculates the lowest common multiple (lcm) of an array of numbers.
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));
-};
-// arrayLcm([1,2,3,4,5]) -> 60
-// arrayLcm([4,8,12]) -> 24
+ 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
Returns the maximum value in an array.
Use Math.max() combined with the spread operator (...) to get the maximum value in the array.
const arrayMax = arr => Math.max(...arr);
-// arrayMax([10, 1, 5]) -> 10
+arrayMax([10, 1, 5]) // 10
Returns the minimum value in an array.
Use Math.min() combined with the spread operator (...) to get the minimum value in the array.
const arrayMin = arr => Math.min(...arr);
-// arrayMin([10, 1, 5]) -> 1
+arrayMin([10, 1, 5]) // 1
Chunks an array into smaller arrays of a specified size.
@@ -352,19 +352,22 @@ UseArray.slice() to map each element of the new array to a chunk t
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]]
+chunk([1,2,3,4,5], 2) // [[1,2],[3,4],[5]]
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 ]
+compact([0, 1, false, 2, '', 3, 'a', 'e'*23, NaN, 's', 34]) // [ 1, 2, 3, 'a', 's', 34 ]
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, value) => arr.reduce((a, v) => v === value ? a + 1 : a + 0, 0);
-// countOccurrences([1,1,2,1,2,3], 1) -> 3
+countOccurrences([1,1,2,1,2,3], 1) // 3
Deep flattens an array.
@@ -372,25 +375,29 @@ If the original array can't be split evenly, the final chunk will contain the re UseArray.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]
+deepFlatten([1,[2],[[3],4],5]) // [1,2,3,4,5]
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]
+difference([1,2,3], [1,2,4]) // [3]
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)));
-// differenceWith([1, 1.2, 1.5, 3], [1.9, 3], (a,b) => Math.round(a) == Math.round(b)) -> [1, 1.2]
+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]
Returns all the distinct values of an array.
Use ES6 Set and the ...rest operator to discard all duplicated values.
const distinctValuesOfArray = arr => [...new Set(arr)];
-// distinctValuesOfArray([1,2,2,3,4,4,5]) -> [1,2,3,4,5]
+distinctValuesOfArray([1,2,2,3,4,4,5]) // [1,2,3,4,5]
Removes elements in an array until the passed function returns true. Returns the remaining elements in the array.
dropElements([1, 2, 3, 4], n => n >= 3) // [3,4]
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) -> []
+dropRight([1,2,3]) // [1,2]
+dropRight([1,2,3], 2) // [1]
+dropRight([1,2,3], 42) // []
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 ]
+everyNth([1,2,3,4,5,6], 2) // [ 2, 4, 6 ]
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]
+filterNonUnique([1,2,2,3,4,4,5]) // [1,3,5]
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);
-// flatten([1,[2],3,4]) -> [1,2,3,4]
+const flatten = arr => [ ].concat( ...arr );
+
+flatten([1,[2],3,4]) // [1,2,3,4]
Flattens an array up to the specified depth.
@@ -437,7 +449,8 @@ Omit the second element,depth to flatten only to a depth of
const flattenDepth = (arr, depth = 1) =>
depth != 1 ? arr.reduce((a, v) => a.concat(Array.isArray(v) ? flattenDepth(v, depth - 1) : v), [])
: arr.reduce((a, v) => a.concat(v), []);
-// flattenDepth([1,[2],[[[3],4],5]], 2) -> [1,2,[3],4,5]
+
+flatten([1,[2],3,4]) // [1,2,3,4]
Groups the elements of an array based on the given function.
@@ -446,26 +459,30 @@ UseArray.reduce() to create an object, where the keys are produced
const groupBy = (arr, func) =>
arr.map(typeof func === 'function' ? func : val => val[func])
.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']}
+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']}
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
+head([1,2,3]) // 1
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]
+initial([1,2,3]) // [1,2]
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(h).fill().map(() => Array(w).fill(val));
-// initializeArrayWithRange(2, 2, 0) -> [[0,0], [0,0]]
+initialize2DArray(2, 2, 0) // [[0,0], [0,0]]
Initializes an array containing the numbers in the specified range where start and end are inclusive.
Array.reduce() to create an object, where the keys are produced
You can omit start to use a default value of 0.
const initializeArrayWithRange = (end, start = 0) =>
Array.from({ length: (end + 1) - start }).map((v, i) => i + start);
-// initializeArrayWithRange(5) -> [0,1,2,3,4,5]
-// initializeArrayWithRange(7, 3) -> [3,4,5,6,7]
+initializeArrayWithRange(5) // [0,1,2,3,4,5]
+initializeArrayWithRange(7, 3) // [3,4,5,6,7]
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 value to use a default value of 0.
const initializeArrayWithValues = (n, value = 0) => Array(n).fill(value);
-// initializeArrayWithValues(5, 2) -> [2,2,2,2,2]
+initializeArrayWithValues(5, 2) // [2,2,2,2,2]
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]
+intersection([1,2,3], [4,3,2]) // [2,3]
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
+last([1,2,3]) // 3
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)
+ (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 }
-*/
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 [].
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];
-// nthElement(['a','b','c'],1) -> 'b'
-// nthElement(['a','b','b'],-3) -> 'a'
+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'
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 pair if the key exists in the obj.
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 }
+pick({ 'a': 1, 'b': '2', 'c': 3 }, ['a', 'c']) // { 'a': 1, 'c': 3 }
Mutates the original array to filter out the values specified.
@@ -532,14 +554,14 @@ UseArray.length = 0 to mutate the passed in an array by resetting
arr.length = 0;
pulled.forEach(v => arr.push(v));
};
+
+let myArray1 = ['a', 'b', 'c', 'a', 'b', 'c'];
+pull(myArray1, 'a', 'c');
+console.log(myArray1) // [ 'b', 'b' ]
-// let myArray1 = ['a', 'b', 'c', 'a', 'b', 'c'];
-// pull(myArray1, 'a', 'c');
-// console.log(myArray1) -> [ 'b', 'b' ]
-
-// let myArray2 = ['a', 'b', 'c', 'a', 'b', 'c'];
-// pull(myArray2, ['a', 'c']);
-// console.log(myArray2) -> [ 'b', 'b' ]
+let myArray2 = ['a', 'b', 'c', 'a', 'b', 'c'];
+pull(myArray2, ['a', 'c']);
+console.log(myArray2) // [ 'b', 'b' ]
Mutates the original array to filter out the values at the specified indexes.
@@ -549,17 +571,17 @@ UseArray.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]);
-// let myArray = ['a', 'b', 'c', 'd'];
-// let pulled = pullAtIndex(myArray, [1, 3]);
-
-// console.log(myArray); -> [ 'a', 'c' ]
-// console.log(pulled); -> [ 'b', 'd' ]
+console.log(myArray); // [ 'a', 'c' ]
+console.log(pulled); // [ 'b', 'd' ]
Mutates the original array to filter out the values specified. Returns the removed elements.
@@ -573,13 +595,12 @@ UseArray.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 myArray = ['a', 'b', 'c', 'd'];
let pulled = pullAtValue(myArray, ['b', 'd']);
-console.log(myArray); -> [ 'a', 'c' ]
-console.log(pulled); -> [ 'b', 'd' ]
-*/
+console.log(myArray); // [ 'a', 'c' ]
+console.log(pulled); // [ 'b', 'd' ]
Removes elements from an array for which the given function returns false.
func is invoked with three arguments (value, index, array
arr.splice(arr.indexOf(val), 1); return acc.concat(val);
}, [])
: [];
-// remove([1, 2, 3, 4], n => n % 2 == 0) -> [2, 4]
+
+remove([1, 2, 3, 4], n => n % 2 == 0) // [2, 4]
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
+sample([3, 7, 9, 11]) // 9
Randomizes the order of the values of an array, returning a new array.
@@ -610,15 +633,17 @@ This method also works with strings. } return arr; }; -// const foo = [1,2,3] -// shuffle(foo) -> [2,3,1] -// console.log(foo) -> [1,2,3] + +const foo = [1,2,3]
+shuffle(foo) // [2,3,1]
+console.log(foo) // [1,2,3]
Returns an array of elements that appear in both arrays.
Use filter() to remove values that are not part of values, determined using includes().
const similarity = (arr, values) => arr.filter(v => values.includes(v));
-// similarity([1,2,3], [1,2,4]) -> [1,2]
+similarity([1,2,3], [1,2,4]) // [1,2]
Returns the symmetric difference between two arrays.
@@ -626,42 +651,48 @@ This method also works with strings.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([1,2,3], [1,2,4]) // [3,4]
Returns all elements in an array except for the first one.
Return arr.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]
+tail([1,2,3]) // [2,3]
+tail([1]) // [1]
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) -> []
+take([1, 2, 3], 5) // [1, 2, 3]
+take([1, 2, 3], 0) // []
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]
+takeRight([1, 2, 3], 2) // [ 2, 3 ]
+takeRight([1, 2, 3]) // [3]
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]
+union([1,2,3], [4,3,2]) // [1,2,3,4]
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]
+without([2, 1, 2, 3], 1, 2) // [3]
Creates an array of elements, grouped based on the position in the original arrays.
@@ -671,45 +702,51 @@ 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]);
- });
-};
-// 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]]
+ 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]]
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}
+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}
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>${item}</li>`);
-// arrayToHtmlList(['item 1', 'item 2'],'myListID')
+const arrayToHtmlList = (arr, listID) => arr.map(item => document.querySelector("#"+listID).innerHTML+=`<li>${item}</li>`);
+
+arrayToHtmlList(['item 1', 'item 2'],'myListID')
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
+// bottomVisible() // true
Returns the current URL.
Use window.location.href to get current URL.
const currentURL = () => window.location.href;
-// currentUrl() -> 'https://google.com'
+currentUrl() // 'https://google.com'
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"
-// detectDeviceType() -> "Desktop"
+const detectDeviceType = () => /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ? "Mobile" : "Desktop";
+
+detectDeviceType() // "Mobile"
+detectDeviceType() // "Desktop"
Returns true if the element specified is visible in the viewport, false otherwise.
// 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)
Returns the scroll position of the current page.
@@ -736,7 +774,8 @@ You can omitel 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}
+getScrollPosition() // {x: 0, y: 200}
Returns an object containing the parameters of the current URL.
@@ -746,7 +785,8 @@ Passlocation.search as the argument to apply to the current
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('http://url.com/page?name=Adam&surname=Smith') // {name: 'Adam', surname: 'Smith'}
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.
@@ -761,7 +801,8 @@ Passlocation.search as the argument to apply to the current
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')
+
+redirect('https://google.com')
Smooth-scrolls to the top of the page.
@@ -774,14 +815,16 @@ Scroll by a fraction of the distance from the top. Usewindow.requestAnima
window.scrollTo(0, c - c / 8);
}
};
-// scrollToTop()
+
+scrollToTop()
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
+getDaysDiffBetweenDates(new Date("2017-12-13"), new Date("2017-12-22")) // 9
Converts a JSON object to a date.
@@ -790,14 +833,16 @@ Scroll by a fraction of the distance from the top. Usewindow.requestAnima
const dt = new Date(parseInt(arr.toString().substr(6)));
return `${dt.getDate()}/${dt.getMonth() + 1}/${dt.getFullYear()}`;
};
-// JSONToDate(/Date(1489525200000)/) -> "14/3/2017"
+
+JSONToDate(/Date(1489525200000)/) // "14/3/2017"
Converts a date from American format to English format.
Use Date.toISOString(), split('T') and replace() to convert a date from American format to the English format.
Throws an error if the passed time cannot be converted to a date.
const toEnglishDate = (time) => { try { return new Date(time).toISOString().split('T')[0].replace(/-/g, '/'); } catch (e) {} };
-// toEnglishDate('09/21/2010') -> '21/09/2010'
+toEnglishDate('09/21/2010') // '21/09/2010'
Results in a string representation of tomorrow's date.
@@ -810,25 +855,23 @@ Use new Date() to get today's date, adding 86400000 of
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(); };
-/*
-chainAsync([
+chainAsync([
next => { console.log('0 seconds'); setTimeout(next, 1000); },
next => { console.log('1 second'); setTimeout(next, 1000); },
next => { console.log('2 seconds'); }
])
-*/
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 add5 = x => x + 5
const multiply = (x, y) => x * y
const multiplyAndAdd5 = compose(add5, multiply)
-multiplyAndAdd5(5, 2) -> 15
-*/
+multiplyAndAdd5(5, 2) // 15
Curries a function.
@@ -840,83 +883,92 @@ If you want to curry a function that accepts a variable number of arguments (a v 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 + +curry(Math.pow)(2)(10) // 1024
+curry(Math.min, 3)(10)(50)(2) // 2
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)
+functionName(Math.max) // max (logged in debug channel of console)
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
+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
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() {
+async function sleepyWork() {
console.log('I\'m going to sleep for 1 second.');
await sleep(1000);
console.log('I woke up after 1 second.');
}
-*/
Negates a predicate function.
Take a predicate function and apply not to it with its arguments.
const negate = func => (...args) => !func(...args);
-// filter([1, 2, 3, 4, 5, 6], negate(isEven)) -> [1, 3, 5]
-// negate(isOdd)(1) -> false
+filter([1, 2, 3, 4, 5, 6], negate(isEven)) // [1, 3, 5]
+negate(isOdd)(1) // false
Returns the average of an array of 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 arrayAverage = arr => arr.reduce((acc, val) => acc + val, 0) / arr.length;
-// arrayAverage([1,2,3]) -> 2
+arrayAverage([1,2,3]) // 2
Returns the sum of an array of numbers.
Use Array.reduce() to add each value to an accumulator, initialized with a value of 0.
const arraySum = arr => arr.reduce((acc, val) => acc + val, 0);
-// arraySum([1,2,3,4]) -> 10
+arraySum([1,2,3,4]) // 10
Clamps num within the inclusive range specified by the boundary values a and b
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
-// clampNumber(3, 2, 4) -> 3
+clampNumber(2, 3, 5) // 3
+clampNumber(1, -1, -5) // -1
+clampNumber(3, 2, 4) // 3
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
-// collatz(5) --> 16
+collatz(8) // 4
+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));
-// digitize(2334) -> [2, 3, 3, 4]
+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]
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
+distance(1,1, 2,3) // 2.23606797749979
Calculates the factorial of a number.
@@ -927,7 +979,8 @@ Throws an exception ifn is a negative number.
const factorial = n =>
n < 0 ? (() => { throw new TypeError('Negative numbers are not allowed!'); })()
: n <= 1 ? 1 : n * factorial(n - 1);
-// factorial(6) -> 720
+factorial(6) // 720
Generates an array, containing the Fibonacci sequence, up until the nth term.
@@ -935,14 +988,16 @@ Throws an exception ifn is a negative number.
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(5) -> [0,1,1,2,3]
+factorial(6) // 720
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
+ Math.ceil(Math.log(num * Math.sqrt(5) + 1/2) / Math.log((Math.sqrt(5)+1)/2));
+fibonacciCountUntilNum(10) // 7
Generates an array, containing the Fibonacci sequence, up until the nth term.
@@ -952,8 +1007,9 @@ 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), []);
-};
-// fibonacciUntilNum(15) -> [0,1,1,2,3,5,8,13]
+}
+fibonacciCountUntilNum(10) // 7
Calculates the greatest common divisor between two numbers.
@@ -961,7 +1017,8 @@ Uses a mathematical formula to calculate the length of the array required. Base case is wheny equals 0. In this case, return x.
Otherwise, return the GCD of y and the remainder of the division x/y.
const gcd = (x, y) => !y ? x : gcd(y, x % y);
-// gcd (8, 36) -> 4
+gcd (8, 36) // 4
Calculates the Hamming distance between two values.
@@ -969,42 +1026,47 @@ Otherwise, return the GCD ofy and the remainder of the division match(/1/g).
const hammingDistance = (num1, num2) =>
((num1 ^ num2).toString(2).match(/1/g) || '').length;
-// hammingDistance(2,3) -> 1
+hammingDistance(2,3) // 1
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);
-};
-// inRange(3, 2, 5) -> true
-// inRange(3, 4) -> true
-// inRange(2, 3, 5) -> false
-// inrange(3, 2) -> false
+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
+inRange(2, 3, 5) // false
+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)((digits + '').split(''));
-// isArmstrongNumber(1634) -> true
-// isArmstrongNumber(371) -> true
-// isArmstrongNumber(56) -> false
+ ( arr => arr.reduce( ( a, d ) => a + Math.pow( parseInt( d ), arr.length ), 0 ) == digits ? true : false )( ( digits+'' ).split( '' ) );
+isArmstrongNumber(1634) // true
+isArmstrongNumber(371) // true
+isArmstrongNumber(56) // false
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
+isDivisible(6,3) // true
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
+isEven(3) // false
Checks if the provided integer is a prime number.
@@ -1015,8 +1077,9 @@ Returnfalse if any of them divides the given number, else return <
for (var i = 2; i * i <= boundary; i++) if (num % i == 0) return false;
return num >= 2;
};
-// isPrime(11) -> true
-// isPrime(12) -> false
+
+isPrime(11) // true
+isPrime(12) // false
Returns the least common multiple of two numbers.
@@ -1026,7 +1089,8 @@ The GCD formula uses recursion. const gcd = (x, y) => !y ? x : gcd(y, x % y); return Math.abs(x * y) / (gcd(x, y)); }; -// lcm(12,7) -> 84 + +lcm(12,7) // 84
Returns the median of an array of numbers.
@@ -1036,8 +1100,9 @@ Return the number at the midpoint iflength is odd, otherwise the a
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
-// median([0,10,-2,7]) -> 3.5
+
+median([5,6,50,1,-5]) // 5
+median([0,10,-2,7]) // 3.5
Returns true if the given string is a palindrome, false otherwise.
split('') into individual characters, reverse(),
const s = str.toLowerCase().replace(/[\W_]/g,'');
return s === s.split('').reverse().join('');
}
-// palindrome('taco cat') -> true
+
+palindrome('taco cat') // true
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
+percentile([1,2,3,4,5,6,7,8,9,10], 6) // 55
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]]
+powerset([1,2]) // [[], [1], [2], [2,1]]
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]
+}
+primes(10) // [2,3,5,7]
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
+randomIntegerInRange(0, 5) // 2
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
+randomNumberInRange(2,10) // 6.0211363285087005
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-${decimals}`);
-// round(1.005, 2) -> 1.01
+const round = (n, decimals=0) => Number(`${Math.round(`${n}e${decimals}`)}e-${decimals}`);
+
+round(1.005, 2) // 1.01
This algorithm is a simple hash-algorithm that hashes it input string s into a whole number.
standardDeviation([10,2,38,23,38,23,21]) // 13.284434142114991 (sample)
+standardDeviation([10,2,38,23,38,23,21], true) // 12.29899614287479 (population)
window.speechSynthesis.speak() to play the message.
msg.voice = window.speechSynthesis.getVoices()[0];
window.speechSynthesis.speak(msg);
};
-// speechSynthesis('Hello, World') -> plays the message
+
+speechSynthesis('Hello, World') // // plays the message
Writes a JSON object to a file.
Use fs.writeFile(), template literals and JSON.stringify() to write a json object to a .json file.
const fs = require('fs');
-const JSONToFile = (obj, filename) => fs.writeFile(`${filename}.json`, JSON.stringify(obj, null, 2));
-// JSONToFile({test: "is passed"}, 'testJsonFile') -> writes the object to 'testJsonFile.json'
+const JSONToFile = (obj, filename) => fs.writeFile(`${filename}.json`, JSON.stringify(obj, null, 2))
+JSONToFile({test: "is passed"}, 'testJsonFile') // writes the object to 'testJsonFile.json'
Returns an array of lines from the specified file.
@@ -1148,16 +1223,25 @@ const JSONToFile = (obj, filename) => fs.writeFile(`${filename}.json`, JSON.s convert buffer to string usingtoString(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).toString('UTF8').split(/\r?\n/);
-/*
- contents of test.txt :
- line1
- line2
- line3
- ___________________________
- let arr = readFileLines('test.txt')
- console.log(arr) // -> ['line1', 'line2', 'line3']
- */
+const readFileLines = filename => fs.readFileSync(filename).toString('UTF8').split('\n');
+/*
+contents of test.txt :
+ line1
+ line2
+ line3
+ ___________________________
+*/
+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']
childIndicator) it will search d
});
return obj;
};
-/*
- const testObj = {a: 1, b: 2, children: {a: 1, b: 2}}
- cleanObj(testObj, ["a"],"children") // { a: 1, children : { a: 1}}
-*/
+
+const testObj = {a: 1, b: 2, children: {a: 1, b: 2}}
+cleanObj(testObj, ["a"],"children") // { a: 1, children : { a: 1}}
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}
+objectFromPairs([['a',1],['b',2]]) // {a: 1, b: 2}
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]])
+objectToPairs({a: 1, b: 2}) // [['a',1],['b',2]])
Returns a sorted array of objects ordered by properties and orders.
@@ -1205,37 +1290,36 @@ If no orders array is passed it sort by 'asc' by default. return acc; }, 0) ); -/* -const users = [{ 'name': 'fred', 'age': 48 },{ 'name': 'barney', 'age': 36 }, + +const users = [{ 'name': 'fred', 'age': 48 },{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 },{ 'name': 'barney', 'age': 34 }];
-orderby(users, ['name', 'age'], ['asc', 'desc']) -> [{name: 'barney', age: 36}, {name: 'barney', age: 34}, {name: 'fred', age: 48}, {name: 'fred', age: 40}]
-orderby(users, ['name', 'age']) -> [{name: 'barney', age: 34}, {name: 'barney', age: 36}, {name: 'fred', age: 40}, {name: 'fred', age: 48}]
-*/
+orderby(users, ['name', 'age'], ['asc', 'desc']) // [{name: 'barney', age: 36}, {name: 'barney', age: 34}, {name: 'fred', age: 48}, {name: 'fred', age: 40}]
+orderby(users, ['name', 'age']) // [{name: 'barney', age: 34}, {name: 'barney', age: 36}, {name: 'fred', age: 40}, {name: 'fred', age: 48}]
Retrieve a property that indicated by the selector from an object.
If the property does not exists returns undefined.
const select = (from, selector) =>
selector.split('.').reduce((prev, cur) => prev && prev[cur], from);
-
-// const obj = {selector: {to: {val: 'val to select'}}};
-// select(obj, 'selector.to.val'); -> 'val to select'
+const obj = {selector: {to: {val: 'val to select'}}};
+select(obj, 'selector.to.val'); // 'val to select'
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 a = { x: true, y: 1 };
const b = shallowClone(a);
-a === b -> false
-*/
+a === b // false
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
+truthCheckCollection([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}], "sex") // true
length equal to 2 or 1
return str.split('').reduce((acc, letter, i) =>
acc.concat(anagrams(str.slice(0, i) + str.slice(i + 1)).map(val => letter + val)), []);
};
-// anagrams('abc') -> ['abc','acb','bac','bca','cab','cba']
+
+anagrams('abc') // ['abc','acb','bac','bca','cab','cba']
Capitalizes the first letter of a string.
@@ -1257,27 +1342,31 @@ Base cases are for stringlength equal to 2 or 1
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('myName') -> 'MyName'
-// capitalize('myName', true) -> 'Myname'
+
+capitalize('fooBar') // 'FooBar'
+capitalize('fooBar', true) // 'Foobar'
Capitalizes the first letter of every word in a string.
Use replace() to match the first character of each word and toUpperCase() to capitalize it.
const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());
-// capitalizeEveryWord('hello world!') -> 'Hello World!'
+capitalizeEveryWord('hello world!') // 'Hello World!'
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]/ig) || []).length;
-// countVowels('foobar') -> 3
-// countVowels('gym') -> 0
+countVowels('foobar') // 3
+countVowels('gym') // 0
Escapes a string to use in a regular expression.
Use replace() to escape special characters.
const escapeRegExp = str => str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
-// escapeRegExp('(test)') -> \\(test\\)
+escapeRegExp('(test)') // \\(test\\)
Converts a string from camelcase.
@@ -1286,32 +1375,36 @@ 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').toLowerCase();
-// fromCamelCase('someDatabaseFieldName', ' ') -> 'some database field name'
-// fromCamelCase('someLabelThatNeedsToBeCamelized', '-') -> 'some-label-that-needs-to-be-camelized'
-// fromCamelCase('someJavascriptProperty', '_') -> 'some_javascript_property'
+fromCamelCase('someDatabaseFieldName', ' ') // 'some database field name'
+fromCamelCase('someLabelThatNeedsToBeCamelized', '-') // 'some-label-that-needs-to-be-camelized'
+fromCamelCase('someJavascriptProperty', '_') // 'some_javascript_property'
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;
-};
-// repeatString("abc",3) -> 'abcabcabc'
-// repeatString("abc") -> 'abcabc'
+const repeatString = (str="",num=2) => {
+ return num >= 0 ? str.repeat(num) : str;
+}
+
+repeatString("abc",3) // 'abcabcabc'
+repeatString("abc") // 'abcabc'
Reverses a string.
Use split('') and Array.reverse() to reverse the order of the characters in the string.
Combine characters to get a string using join('').
const reverseString = str => str.split('').reverse().join('');
-// reverseString('foobar') -> 'raboof'
+reverseString('foobar') // 'raboof'
Alphabetically sorts the characters in a string.
Split the string using split(''), Array.sort() utilizing localeCompare(), recombine using join('').
const sortCharactersInString = str =>
str.split('').sort((a, b) => a.localeCompare(b)).join('');
-// sortCharactersInString('cabbage') -> 'aabbceg'
+sortCharactersInString('cabbage') // 'aabbceg'
Converts a string to camelcase.
@@ -1321,12 +1414,13 @@ For more detailed explanation of this Regex, toCamelCase("some_database_field_name") // 'someDatabaseFieldName' +toCamelCase("Some label that needs to be camelized") // 'someLabelThatNeedsToBeCamelized' +toCamelCase("some-javascript-property") // 'someJavascriptProperty' +toCamelCase("some-mixed_string with spaces_underscores-and-hyphens") // 'someMixedStringWithSpacesUnderscoresAndHyphens'Converts a string to kebab case.
@@ -1336,11 +1430,12 @@ For more detailed explanation of this Regex, toKebabCase("camelCase") // 'camel-case' +toKebabCase("some text") // 'some-text' +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"Converts a string to snake case.
@@ -1351,12 +1446,13 @@ For more detailed explanation of this Regex, toSnakeCase("camelCase") // 'camel_case' +toSnakeCase("some text") // 'some_text' +toSnakeCase("some-javascript-property") // 'some_javascript_property' +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"Truncates a string up to a specified length.
@@ -1364,45 +1460,51 @@ For more detailed explanation of this Regex, const truncateString = (str, num) => str.length > num ? str.slice(0, num > 3 ? num - 3 : num) + '...' : str; -// truncateString('boomerang', 7) -> 'boom...' + +truncateString('boomerang', 7) // 'boom...'
Converts a given string into an array of words.
Use String.split() with a supplied pattern (defaults to non-alpha as a regex) to convert to an array of strings. Use Array.filter() to remove any empty strings.
Omit the second argument to use the default regex.
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"]
+words("I love javaScript!!") // ["I", "love", "javaScript"]
+words("python, javaScript & coffee") // ["python", "javaScript", "coffee"]
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") -> ""
+const coalesce = (...args) => args.find(_ => ![undefined, null].includes(_))
+
+coalesce(null,undefined,"",NaN, "Waldo") // ""
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"
+const customCoalesce = coalesceFactory(_ => ![null, undefined, "", NaN].includes(_))
+customCoalesce(undefined, null, NaN, "", "Waldo") // "Waldo"
Extends a 3-digit color code to a 6-digit color code.
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('');
-// extendHex('#03f') -> '#0033ff'
-// extendHex('05a') -> '#0055aa'
+ '#' + shortHex.slice(shortHex.startsWith('#') ? 1 : 0).split('').map(x => x+x).join('')
+extendHex('#03f') // '#0033ff'
+extendHex('05a') // '#0055aa'
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"
+getType(new Set([1,2,3])) // "set"
Converts a color code to a rgb() or rgba() string if alpha value is provided.
hexToRGB('#27ae60ff') // 'rgba(39, 174, 96, 255)'
+hexToRGB('27ae60') // 'rgb(39, 174, 96)'
+hexToRGB('#fff') // 'rgb(255, 255, 255)'
Checks if the given argument is an array.
Use Array.isArray() to check if a value is classified as an array.
const isArray = val => !!val && Array.isArray(val);
-// isArray(null) -> false
-// isArray([1]) -> true
+isArray(null) // false
+isArray([1]) // true
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
+isBoolean(null) // false
+isBoolean(false) // true
Checks if the given argument is a function.
Use typeof to check if a value is classified as a function primitive.
const isFunction = val => val && typeof val === 'function';
-// isFunction('x') -> false
-// isFunction(x => x) -> true
+isFunction('x') // false
+isFunction(x => x) // true
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
+isNumber('1') // false
+isNumber(1) // true
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) -> false
-// isString('10') -> true
+isString(10) // false
+isString('10') // true
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('x') -> false
-// isSymbol(Symbol('x')) -> true
+isSymbol('x') // false
+isSymbol(Symbol('x')) // true
Generates a random hexadecimal color code.
@@ -1472,15 +1581,17 @@ Omit the second argument to use the default regex. return '#' + (n.length !== 6 ? (Math.random() * 0xf | 0).toString(16) + n : n); }; -// randomHexColorCode() -> "#e34155" -// randomHexColorCode() -> "#fd73a6" -// randomHexColorCode() -> "#4144c6" + +randomHexColorCode() // "#e34155"
+randomHexColorCode() // "#fd73a6"
+randomHexColorCode() // "#4144c6"
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 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'
+RGBToHex(255, 165, 1) // 'ffa501'
Measures the time taken by a function to execute.
@@ -1489,13 +1600,15 @@ Omit the second argument to use the default regex. console.time('timeTaken'); const r = callback(); console.timeEnd('timeTaken'); return r; }; -// timeTaken(() => Math.pow(2, 10)) -> 1024 -// (logged): timeTaken: 0.02099609375ms + +timeTaken(() => Math.pow(2, 10)) // 1024
+(logged): timeTaken: 0.02099609375ms
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) -> "12,305,030,388.9087"
+const toDecimalMark = num => num.toLocaleString("en-US");
+
+toDecimalMark(12305030388.9087) // "12,305,030,388.9087"
Adds an ordinal suffix to a number.
@@ -1508,7 +1621,8 @@ If digit is found in teens pattern, use teens ordinal. tPattern = [11, 12, 13, 14, 15, 16, 17, 18, 19]; return oPattern.includes(digits[0]) && !tPattern.includes(digits[1]) ? int + ordinals[digits[0] - 1] : int + ordinals[3]; }; -// toOrdinalSuffix("123") -> "123rd" + +toOrdinalSuffix("123") // "123rd"
Generates a UUID.
@@ -1517,7 +1631,8 @@ If digit is found in teens pattern, use teens ordinal. ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c => (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16) ); -// UUIDGenerator() -> '7982fcfe-5721-4632-bede-6000885be57d' + +UUIDGenerator() // '7982fcfe-5721-4632-bede-6000885be57d'
Returns true if the given value is a number, false otherwise.
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
+validateNumber('10') // true