From 0219b6bc68a226faec4675c1f38ebd75dd5d6d38 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Stefan=20Feje=C5=A1?= Date: Mon, 25 Dec 2017 14:51:48 +0100 Subject: [PATCH] builder --- README.md | 1029 ++++++++++++++++++++++++++++++++++++----------------- 1 file changed, 699 insertions(+), 330 deletions(-) diff --git a/README.md b/README.md index a29b99093..3269733e7 100644 --- a/README.md +++ b/README.md @@ -1,6 +1,6 @@ ![Logo](/logo.png) -# 30 seconds of code +# 30 seconds of code [![License](https://img.shields.io/badge/license-CC0--1.0-blue.svg)](https://github.com/Chalarangelo/30-seconds-of-code/blob/master/LICENSE) [![Gitter chat](https://badges.gitter.im/gitterHQ/gitter.png)](https://gitter.im/30-seconds-of-code/Lobby) [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat-square)](http://makeapullrequest.com) [![Travis Build](https://travis-ci.org/Chalarangelo/30-seconds-of-code.svg?branch=master)](https://travis-ci.org/Chalarangelo/30-seconds-of-code) [![Insight.io](https://img.shields.io/badge/insight.io-Ready-brightgreen.svg)](https://insight.io/github.com/Chalarangelo/30-seconds-of-code/tree/master/?source=0) [![js-semistandard-style](https://img.shields.io/badge/code%20style-semistandard-brightgreen.svg?style=flat-square)](https://github.com/Flet/semistandard) > Curated collection of useful Javascript snippets that you can understand in 30 seconds or less. @@ -186,13 +186,14 @@ Given a key and a set of arguments, call them when given a context. Primarily us Use a closure to call a stored key with stored arguments. ```js -const call = (key, ...args) => context => context[ key ](...args); -/* +const call = ( key, ...args ) => context => context[ key ]( ...args ); +``` + +```js 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 ] -*/ -``` +``` [⬆ back to top](#table-of-contents) @@ -203,15 +204,16 @@ 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. ```js -const collectInto = fn => (...args) => fn(args); -/* +const collectInto = fn => ( ...args ) => fn( args ); +``` + +```js 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) -*/ -``` +``` [⬆ back to top](#table-of-contents) @@ -222,8 +224,10 @@ 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. ```js -const flip = fn => (...args) => fn(args.pop(), ...args); -/* +const flip = fn => (...args) => fn(args.pop(), ...args) +``` + +```js let a = {name: 'John Smith'} let b = {} const mergeFrom = flip(Object.assign) @@ -231,27 +235,7 @@ let mergePerson = mergeFrom.bind(null, a) mergePerson(b) // == b b = {} Object.assign(b, a) // == b -*/ -``` - -[⬆ back to top](#table-of-contents) - -### 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. - -```js -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 -*/ -``` +``` [⬆ back to top](#table-of-contents) @@ -271,8 +255,11 @@ const promisify = func => 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 +``` + +```js +const delay = promisify((d, cb) => setTimeout(cb, d)) +delay(2000).then(() => console.log('Hi!')) -> // Promise resolves after 2s ``` [⬆ back to top](#table-of-contents) @@ -285,12 +272,13 @@ Use closures and the spread operator (`...`) to map the array of arguments to th ```js const spreadOver = fn => argsArr => fn(...argsArr); -/* +``` + +```js const arrayMax = spreadOver(Math.max) -arrayMax([1,2,3]) // -> 3 -arrayMax([1,2,4]) // -> 4 -*/ -``` +arrayMax([1,2,3]) -> 3 +arrayMax([1,2,4]) -> 4 +``` [⬆ back to top](#table-of-contents) ## Array @@ -304,10 +292,13 @@ Use `Array.reduce()` and the `gcd` formula (uses recursion) to calculate the gre ```js 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)); +} +``` + +```js +arrayGcd([1,2,3,4,5]) -> 1 +arrayGcd([4,8,12]) -> 4 ``` [⬆ back to top](#table-of-contents) @@ -321,11 +312,14 @@ Use `Array.reduce()` and the `lcm` formula (uses recursion) to calculate the low ```js 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)); +} +``` + +```js +arrayLcm([1,2,3,4,5]) -> 60 +arrayLcm([4,8,12]) -> 24 ``` [⬆ back to top](#table-of-contents) @@ -338,7 +332,10 @@ Use `Math.max()` combined with the spread operator (`...`) to get the maximum va ```js const arrayMax = arr => Math.max(...arr); -// arrayMax([10, 1, 5]) -> 10 +``` + +```js +arrayMax([10, 1, 5]) -> 10 ``` [⬆ back to top](#table-of-contents) @@ -351,7 +348,10 @@ Use `Math.min()` combined with the spread operator (`...`) to get the minimum va ```js const arrayMin = arr => Math.min(...arr); -// arrayMin([10, 1, 5]) -> 1 +``` + +```js +arrayMin([10, 1, 5]) -> 1 ``` [⬆ back to top](#table-of-contents) @@ -367,7 +367,10 @@ If the original array can't be split evenly, the final chunk will contain the re ```js 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]] +``` + +```js +chunk([1,2,3,4,5], 2) -> [[1,2],[3,4],[5]] ``` [⬆ back to top](#table-of-contents) @@ -380,7 +383,10 @@ Use `Array.filter()` to filter out falsey values (`false`, `null`, `0`, `""`, `u ```js const compact = arr => arr.filter(Boolean); -// compact([0, 1, false, 2, '', 3, 'a', 'e'*23, NaN, 's', 34]) -> [ 1, 2, 3, 'a', 's', 34 ] +``` + +```js +compact([0, 1, false, 2, '', 3, 'a', 'e'*23, NaN, 's', 34]) -> [ 1, 2, 3, 'a', 's', 34 ] ``` [⬆ back to top](#table-of-contents) @@ -393,7 +399,10 @@ Use `Array.reduce()` to increment a counter each time you encounter the specific ```js const countOccurrences = (arr, value) => arr.reduce((a, v) => v === value ? a + 1 : a + 0, 0); -// countOccurrences([1,1,2,1,2,3], 1) -> 3 +``` + +```js +countOccurrences([1,1,2,1,2,3], 1) -> 3 ``` [⬆ back to top](#table-of-contents) @@ -408,7 +417,10 @@ Recursively flatten each element that is an array. ```js const deepFlatten = arr => [].concat(...arr.map(v => Array.isArray(v) ? deepFlatten(v) : v)); -// deepFlatten([1,[2],[[3],4],5]) -> [1,2,3,4,5] +``` + +```js +deepFlatten([1,[2],[[3],4],5]) -> [1,2,3,4,5] ``` [⬆ back to top](#table-of-contents) @@ -421,7 +433,10 @@ Create a `Set` from `b`, then use `Array.filter()` on `a` to only keep values no ```js const difference = (a, b) => { const s = new Set(b); return a.filter(x => !s.has(x)); }; -// difference([1,2,3], [1,2,4]) -> [3] +``` + +```js +difference([1,2,3], [1,2,4]) -> [3] ``` [⬆ back to top](#table-of-contents) @@ -433,8 +448,11 @@ Filters out all values from an array for which the comparator function does not Use `Array.filter()` and `Array.find()` to find the appropriate values. ```js -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))) +``` + +```js +differenceWith([1, 1.2, 1.5, 3], [1.9, 3], (a,b) => Math.round(a) == Math.round(b)) -> [1, 1.2] ``` [⬆ back to top](#table-of-contents) @@ -447,7 +465,10 @@ Use ES6 `Set` and the `...rest` operator to discard all duplicated values. ```js const distinctValuesOfArray = arr => [...new Set(arr)]; -// distinctValuesOfArray([1,2,2,3,4,4,5]) -> [1,2,3,4,5] +``` + +```js +distinctValuesOfArray([1,2,2,3,4,4,5]) -> [1,2,3,4,5] ``` [⬆ back to top](#table-of-contents) @@ -464,7 +485,10 @@ const dropElements = (arr, func) => { while (arr.length > 0 && !func(arr[0])) arr = arr.slice(1); return arr; }; -// dropElements([1, 2, 3, 4], n => n >= 3) -> [3,4] +``` + +```js +dropElements([1, 2, 3, 4], n => n >= 3) -> [3,4] ``` [⬆ back to top](#table-of-contents) @@ -477,9 +501,12 @@ Use `Array.slice()` to slice the remove the specified number of elements from th ```js 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) -> [] +``` + +```js +dropRight([1,2,3]) -> [1,2] +dropRight([1,2,3], 2) -> [1] +dropRight([1,2,3], 42) -> [] ``` [⬆ back to top](#table-of-contents) @@ -492,7 +519,10 @@ Use `Array.filter()` to create a new array that contains every nth element of a ```js const everyNth = (arr, nth) => arr.filter((e, i) => i % nth === nth - 1); -// everyNth([1,2,3,4,5,6], 2) -> [ 2, 4, 6 ] +``` + +```js +everyNth([1,2,3,4,5,6], 2) -> [ 2, 4, 6 ] ``` [⬆ back to top](#table-of-contents) @@ -505,7 +535,10 @@ Use `Array.filter()` for an array containing only the unique values. ```js const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i)); -// filterNonUnique([1,2,2,3,4,4,5]) -> [1,3,5] +``` + +```js +filterNonUnique([1,2,2,3,4,4,5]) -> [1,3,5] ``` [⬆ back to top](#table-of-contents) @@ -517,8 +550,11 @@ Flattens an array. Use a new array and concatenate it with the spread input array causing a shallow denesting of any contained arrays. ```js -const flatten = arr => [ ].concat(...arr); -// flatten([1,[2],3,4]) -> [1,2,3,4] +const flatten = arr => [ ].concat( ...arr ); +``` + +```js +flatten([1,[2],3,4]) -> [1,2,3,4] ``` [⬆ back to top](#table-of-contents) @@ -536,7 +572,10 @@ Omit the second element, `depth` to flatten only to a depth of `1` (single flatt 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] +``` + +```js +flatten([1,[2],3,4]) -> [1,2,3,4] ``` [⬆ back to top](#table-of-contents) @@ -552,8 +591,11 @@ Use `Array.reduce()` to create an object, where the keys are produced from the m 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']} +``` + +```js +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']} ``` [⬆ back to top](#table-of-contents) @@ -566,7 +608,10 @@ Use `arr[0]` to return the first element of the passed array. ```js const head = arr => arr[0]; -// head([1,2,3]) -> 1 +``` + +```js +head([1,2,3]) -> 1 ``` [⬆ back to top](#table-of-contents) @@ -579,7 +624,10 @@ Use `arr.slice(0,-1)` to return all but the last element of the array. ```js const initial = arr => arr.slice(0, -1); -// initial([1,2,3]) -> [1,2] +``` + +```js +initial([1,2,3]) -> [1,2] ``` [⬆ back to top](#table-of-contents) @@ -592,7 +640,10 @@ Use `Array.map()` to generate h rows where each is a new array of size w initial ```js const initialize2DArray = (w, h, val = null) => Array(h).fill().map(() => Array(w).fill(val)); -// initializeArrayWithRange(2, 2, 0) -> [[0,0], [0,0]] +``` + +```js +initialize2DArray(2, 2, 0) -> [[0,0], [0,0]] ``` [⬆ back to top](#table-of-contents) @@ -607,8 +658,11 @@ You can omit `start` to use a default value of `0`. ```js 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] +``` + +```js +initializeArrayWithRange(5) -> [0,1,2,3,4,5] +initializeArrayWithRange(7, 3) -> [3,4,5,6,7] ``` [⬆ back to top](#table-of-contents) @@ -622,7 +676,10 @@ You can omit `value` to use a default value of `0`. ```js const initializeArrayWithValues = (n, value = 0) => Array(n).fill(value); -// initializeArrayWithValues(5, 2) -> [2,2,2,2,2] +``` + +```js +initializeArrayWithValues(5, 2) -> [2,2,2,2,2] ``` [⬆ back to top](#table-of-contents) @@ -635,7 +692,10 @@ Create a `Set` from `b`, then use `Array.filter()` on `a` to only keep values co ```js 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] +``` + +```js +intersection([1,2,3], [4,3,2]) -> [2,3] ``` [⬆ back to top](#table-of-contents) @@ -648,7 +708,10 @@ Use `arr.length - 1` to compute the index of the last element of the given array ```js const last = arr => arr[arr.length - 1]; -// last([1,2,3]) -> 3 +``` + +```js +last([1,2,3]) -> 3 ``` [⬆ back to top](#table-of-contents) @@ -661,11 +724,12 @@ Use an anonymous inner function scope to declare an undefined memory space, usin ```js 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), {}) )) ( ); +``` + +```js const squareIt = arr => mapObject(arr, a => a*a) squareIt([1,2,3]) // { 1: 1, 2: 4, 3: 9 } -*/ ``` [⬆ back to top](#table-of-contents) @@ -679,9 +743,12 @@ If the index is out of bounds, return `[]`. Omit the second argument, `n`, to get the first element of the array. ```js -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]; +``` + +```js +nthElement(['a','b','c'],1) -> 'b' +nthElement(['a','b','b'],-3) -> 'a' ``` [⬆ back to top](#table-of-contents) @@ -695,7 +762,10 @@ Use `Array.reduce()` to convert the filtered/picked keys back to an object with ```js 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 } +``` + +```js +pick({ 'a': 1, 'b': '2', 'c': 3 }, ['a', 'c']) -> { 'a': 1, 'c': 3 } ``` [⬆ back to top](#table-of-contents) @@ -716,14 +786,16 @@ const pull = (arr, ...args) => { 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' ] +```js +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' ] ``` [⬆ back to top](#table-of-contents) @@ -734,23 +806,25 @@ 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 +Use `Array.push()` to keep track of pulled values ```js 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]); +```js +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' ] ``` [⬆ back to top](#table-of-contents) @@ -761,7 +835,7 @@ Mutates the original array to filter out the values specified. Returns the remov 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 +Use `Array.push()` to keep track of pulled values ```js const pullAtValue = (arr, pullArr) => { @@ -771,13 +845,14 @@ const pullAtValue = (arr, pullArr) => { arr.length = 0; mutateTo.forEach(v => arr.push(v)); return removed; -}; -/* +} +``` + +```js let myArray = ['a', 'b', 'c', 'd']; let pulled = pullAtValue(myArray, ['b', 'd']); console.log(myArray); -> [ 'a', 'c' ] console.log(pulled); -> [ 'b', 'd' ] -*/ ``` [⬆ back to top](#table-of-contents) @@ -795,7 +870,10 @@ const remove = (arr, func) => arr.splice(arr.indexOf(val), 1); return acc.concat(val); }, []) : []; -// remove([1, 2, 3, 4], n => n % 2 == 0) -> [2, 4] +``` + +```js +remove([1, 2, 3, 4], n => n % 2 == 0) -> [2, 4] ``` [⬆ back to top](#table-of-contents) @@ -809,7 +887,10 @@ This method also works with strings. ```js const sample = arr => arr[Math.floor(Math.random() * arr.length)]; -// sample([3, 7, 9, 11]) -> 9 +``` + +```js +sample([3, 7, 9, 11]) -> 9 ``` [⬆ back to top](#table-of-contents) @@ -821,17 +902,11 @@ Randomizes the order of the values of an array, returning a new array. Uses the Fisher-Yates algoritm to reorder the elements of the array, based on the [Lodash implementation](https://github.com/lodash/lodash/blob/b2ea6b1cd251796dcb5f9700c4911a7b6223920b/shuffle.js), but as a pure function. ```js -const shuffle = ([...arr]) => { - let m = arr.length; - while (m) { - const i = Math.floor(Math.random() * m--); - [arr[m], arr[i]] = [arr[i], arr[m]]; - } - return arr; -}; -// const foo = [1,2,3] -// shuffle(foo) -> [2,3,1] -// console.log(foo) -> [1,2,3] +const shuffle = arr => arr.sort(() => Math.random() - 0.5); +``` + +```js +shuffle([1,2,3]) -> [2,3,1] ``` [⬆ back to top](#table-of-contents) @@ -844,7 +919,10 @@ Use `filter()` to remove values that are not part of `values`, determined using ```js const similarity = (arr, values) => arr.filter(v => values.includes(v)); -// similarity([1,2,3], [1,2,4]) -> [1,2] +``` + +```js +similarity([1,2,3], [1,2,4]) -> [1,2] ``` [⬆ back to top](#table-of-contents) @@ -859,8 +937,11 @@ Create a `Set` from each array, then use `Array.filter()` on each of them to onl 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] +} +``` + +```js +symmetricDifference([1,2,3], [1,2,4]) -> [3,4] ``` [⬆ back to top](#table-of-contents) @@ -873,8 +954,11 @@ Return `arr.slice(1)` if the array's `length` is more than `1`, otherwise, retur ```js const tail = arr => arr.length > 1 ? arr.slice(1) : arr; -// tail([1,2,3]) -> [2,3] -// tail([1]) -> [1] +``` + +```js +tail([1,2,3]) -> [2,3] +tail([1]) -> [1] ``` [⬆ back to top](#table-of-contents) @@ -887,8 +971,11 @@ Use `Array.slice()` to create a slice of the array with `n` elements taken from ```js const take = (arr, n = 1) => arr.slice(0, n); -// take([1, 2, 3], 5) -> [1, 2, 3] -// take([1, 2, 3], 0) -> [] +``` + +```js +take([1, 2, 3], 5) -> [1, 2, 3] +take([1, 2, 3], 0) -> [] ``` [⬆ back to top](#table-of-contents) @@ -901,8 +988,11 @@ Use `Array.slice()` to create a slice of the array with `n` elements taken from ```js const takeRight = (arr, n = 1) => arr.slice(arr.length - n, arr.length); -// takeRight([1, 2, 3], 2) -> [ 2, 3 ] -// takeRight([1, 2, 3]) -> [3] +``` + +```js +takeRight([1, 2, 3], 2) -> [ 2, 3 ] +takeRight([1, 2, 3]) -> [3] ``` [⬆ back to top](#table-of-contents) @@ -915,7 +1005,10 @@ Create a `Set` with all values of `a` and `b` and convert to an array. ```js const union = (a, b) => Array.from(new Set([...a, ...b])); -// union([1,2,3], [4,3,2]) -> [1,2,3,4] +``` + +```js +union([1,2,3], [4,3,2]) -> [1,2,3,4] ``` [⬆ back to top](#table-of-contents) @@ -930,7 +1023,10 @@ _(For a snippet that mutates the original array see [`pull`](#pull))_ ```js const without = (arr, ...args) => arr.filter(v => !args.includes(v)); -// without([2, 1, 2, 3], 1, 2) -> [3] +``` + +```js +without([2, 1, 2, 3], 1, 2) -> [3] ``` [⬆ back to top](#table-of-contents) @@ -947,11 +1043,14 @@ If lengths of the argument-arrays vary, `undefined` is used where no value could 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]); + }) +} +``` + +```js +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]] ``` [⬆ back to top](#table-of-contents) @@ -963,9 +1062,12 @@ Given an array of valid property identifiers and an array of values, return an o 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()`. ```js -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 ), {} ) +``` + +```js +zipObject(['a','b','c'], [1,2]) -> {a: 1, b: 2, c: undefined} +zipObject(['a','b'], [1,2,3]) -> {a: 1, b: 2} ``` [⬆ back to top](#table-of-contents) @@ -978,8 +1080,11 @@ Converts the given array elements into `
  • ` tags and appends them to the list Use `Array.map()` and `document.querySelector()` to create a list of html tags. ```js -const arrayToHtmlList = (arr, listID) => arr.map(item => document.querySelector('#' + listID).innerHTML += `
  • ${item}
    • `); -// arrayToHtmlList(['item 1', 'item 2'],'myListID') +const arrayToHtmlList = (arr, listID) => arr.map(item => document.querySelector("#"+listID).innerHTML+=`
  • ${item}
    • `); +``` + +```js +arrayToHtmlList(['item 1', 'item 2'],'myListID') ``` [⬆ back to top](#table-of-contents) @@ -993,6 +1098,9 @@ Use `scrollY`, `scrollHeight` and `clientHeight` to determine if the bottom of t ```js const bottomVisible = () => document.documentElement.clientHeight + window.scrollY >= (document.documentElement.scrollHeight || document.documentElement.clientHeight); +``` + +```js // bottomVisible() -> true ``` @@ -1006,7 +1114,10 @@ Use `window.location.href` to get current URL. ```js const currentURL = () => window.location.href; -// currentUrl() -> 'https://google.com' +``` + +```js +currentUrl() -> 'https://google.com' ``` [⬆ back to top](#table-of-contents) @@ -1018,9 +1129,12 @@ Detects wether the website is being opened in a mobile device or a desktop/lapto Use a regular expression to test the `navigator.userAgent` property to figure out if the device is a mobile device or a desktop/laptop. ```js -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"; +``` + +```js +detectDeviceType() -> "Mobile" +detectDeviceType() -> "Desktop" ``` [⬆ back to top](#table-of-contents) @@ -1043,9 +1157,12 @@ const elementIsVisibleInViewport = (el, partiallyVisible = false) => { ((left > 0 && left < innerWidth) || (right > 0 && right < innerWidth)) : top >= 0 && left >= 0 && bottom <= innerHeight && right <= innerWidth; }; +``` + +```js // 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) +elementIsVisibleInViewport(el) -> false // (not fully visible) +elementIsVisibleInViewport(el, true) -> true // (partially visible) ``` [⬆ back to top](#table-of-contents) @@ -1061,7 +1178,10 @@ 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} +``` + +```js +getScrollPosition() -> {x: 0, y: 200} ``` [⬆ back to top](#table-of-contents) @@ -1078,7 +1198,10 @@ 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'} +``` + +```js +getURLParameters('http://url.com/page?name=Adam&surname=Smith') -> {name: 'Adam', surname: 'Smith'} ``` [⬆ back to top](#table-of-contents) @@ -1107,7 +1230,10 @@ Pass a second argument to simulate a link click (`true` - default) or an HTTP re ```js const redirect = (url, asLink = true) => asLink ? window.location.href = url : window.location.replace(url); -// redirect('https://google.com') +``` + +```js +redirect('https://google.com') ``` [⬆ back to top](#table-of-contents) @@ -1127,7 +1253,10 @@ const scrollToTop = () => { window.scrollTo(0, c - c / 8); } }; -// scrollToTop() +``` + +```js +scrollToTop() ``` [⬆ back to top](#table-of-contents) @@ -1141,7 +1270,10 @@ Calculate the difference (in days) between two `Date` objects. ```js const getDaysDiffBetweenDates = (dateInitial, dateFinal) => (dateFinal - dateInitial) / (1000 * 3600 * 24); -// getDaysDiffBetweenDates(new Date("2017-12-13"), new Date("2017-12-22")) -> 9 +``` + +```js +getDaysDiffBetweenDates(new Date("2017-12-13"), new Date("2017-12-22")) -> 9 ``` [⬆ back to top](#table-of-contents) @@ -1157,7 +1289,10 @@ 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" +``` + +```js +JSONToDate(/Date(1489525200000)/) -> "14/3/2017" ``` [⬆ back to top](#table-of-contents) @@ -1170,8 +1305,12 @@ Use `Date.toISOString()`, `split('T')` and `replace()` to convert a date from Am Throws an error if the passed time cannot be converted to a date. ```js -const toEnglishDate = (time) => { try { return new Date(time).toISOString().split('T')[0].replace(/-/g, '/'); } catch (e) {} }; -// toEnglishDate('09/21/2010') -> '21/09/2010' +const toEnglishDate = (time) => + {try{return new Date(time).toISOString().split('T')[0].replace(/-/g, '/')}catch(e){return}}; +``` + +```js +toEnglishDate('09/21/2010') -> '21/09/2010' ``` [⬆ back to top](#table-of-contents) @@ -1197,13 +1336,14 @@ Loop through an array of functions containing asynchronous events, calling `next ```js const chainAsync = fns => { let curr = 0; const next = () => fns[curr++](next); next(); }; -/* +``` + +```js chainAsync([ next => { console.log('0 seconds'); setTimeout(next, 1000); }, next => { console.log('1 second'); setTimeout(next, 1000); }, next => { console.log('2 seconds'); } ]) -*/ ``` [⬆ back to top](#table-of-contents) @@ -1217,12 +1357,13 @@ The last (rightmost) function can accept one or more arguments; the remaining fu ```js const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args))); -/* +``` + +```js const add5 = x => x + 5 const multiply = (x, y) => x * y const multiplyAndAdd5 = compose(add5, multiply) multiplyAndAdd5(5, 2) -> 15 -*/ ``` [⬆ back to top](#table-of-contents) @@ -1241,8 +1382,11 @@ 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 +``` + +```js +curry(Math.pow)(2)(10) -> 1024 +curry(Math.min, 3)(10)(50)(2) -> 2 ``` [⬆ back to top](#table-of-contents) @@ -1255,7 +1399,30 @@ Use `console.debug()` and the `name` property of the passed method to log the me ```js const functionName = fn => (console.debug(fn.name), fn); -// functionName(Math.max) -> max (logged in debug channel of console) +``` + +```js +functionName(Math.max) -> max (logged in debug channel of console) +``` + +[⬆ back to top](#table-of-contents) + +### pipe + +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. + +```js +const pipeFunctions = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args))); +``` + +```js +const add5 = x => x + 5 +const multiply = (x, y) => x * y +const multiplyAndAdd5 = pipeFunctions(multiply, add5) +multiplyAndAdd5(5, 2) -> 15 ``` [⬆ back to top](#table-of-contents) @@ -1268,8 +1435,11 @@ Use `Array.reduce()` to create a promise chain, where each promise returns the n ```js 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 +``` + +```js +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 ``` [⬆ back to top](#table-of-contents) @@ -1282,13 +1452,14 @@ Delay executing part of an `async` function, by putting it to sleep, returning a ```js const sleep = ms => new Promise(resolve => setTimeout(resolve, ms)); -/* +``` + +```js async function sleepyWork() { console.log('I\'m going to sleep for 1 second.'); await sleep(1000); console.log('I woke up after 1 second.'); } -*/ ``` [⬆ back to top](#table-of-contents) @@ -1302,8 +1473,11 @@ Take a predicate function and apply `not` to it with its arguments. ```js const negate = func => (...args) => !func(...args); -// filter([1, 2, 3, 4, 5, 6], negate(isEven)) -> [1, 3, 5] -// negate(isOdd)(1) -> false +``` + +```js +filter([1, 2, 3, 4, 5, 6], negate(isEven)) -> [1, 3, 5] +negate(isOdd)(1) -> false ``` [⬆ back to top](#table-of-contents) @@ -1317,7 +1491,10 @@ Use `Array.reduce()` to add each value to an accumulator, initialized with a val ```js const arrayAverage = arr => arr.reduce((acc, val) => acc + val, 0) / arr.length; -// arrayAverage([1,2,3]) -> 2 +``` + +```js +arrayAverage([1,2,3]) -> 2 ``` [⬆ back to top](#table-of-contents) @@ -1330,7 +1507,10 @@ Use `Array.reduce()` to add each value to an accumulator, initialized with a val ```js const arraySum = arr => arr.reduce((acc, val) => acc + val, 0); -// arraySum([1,2,3,4]) -> 10 +``` + +```js +arraySum([1,2,3,4]) -> 10 ``` [⬆ back to top](#table-of-contents) @@ -1339,14 +1519,21 @@ const arraySum = arr => arr.reduce((acc, val) => acc + val, 0); Clamps `num` within the inclusive range specified by the boundary values `a` and `b` -If `num` falls within the range, return `num`. +If `lower` is greater than `upper`, swap them. +If `num` falls within the range, return `num`. Otherwise, return the nearest number in the range. ```js -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 +const clampNumber = (num, lower, upper) => { + if(lower > upper) upper = [lower, lower = upper][0]; + return (num>=lower && num<=upper) ? num : ((num < lower) ? lower : upper) +} +``` + +```js +clampNumber(2, 3, 5) -> 3 +clampNumber(1, -1, -5) -> -1 +clampNumber(3, 2, 4) -> 3 ``` [⬆ back to top](#table-of-contents) @@ -1359,8 +1546,11 @@ If `n` is even, return `n/2`. Otherwise, return `3n+1`. ```js const collatz = n => (n % 2 == 0) ? (n / 2) : (3 * n + 1); -// collatz(8) --> 4 -// collatz(5) --> 16 +``` + +```js +collatz(8) -> 4 +collatz(5) -> 16 ``` [⬆ back to top](#table-of-contents) @@ -1373,8 +1563,11 @@ Convert the number to a string, using spread operators in ES6(`[...string]`) bui Use `Array.map()` and `parseInt()` to transform each value to an integer. ```js -const digitize = n => [...'' + n].map(i => parseInt(i)); -// digitize(2334) -> [2, 3, 3, 4] +const digitize = n => [...''+n].map(i => parseInt(i)); +``` + +```js +differenceWith([1, 1.2, 1.5, 3], [1.9, 3], (a,b) => Math.round(a) == Math.round(b)) -> [1, 1.2] ``` [⬆ back to top](#table-of-contents) @@ -1387,7 +1580,10 @@ Use `Math.hypot()` to calculate the Euclidean distance between two points. ```js const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0); -// distance(1,1, 2,3) -> 2.23606797749979 +``` + +```js +distance(1,1, 2,3) -> 2.23606797749979 ``` [⬆ back to top](#table-of-contents) @@ -1405,7 +1601,10 @@ Throws an exception if `n` 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 +``` + +```js +factorial(6) -> 720 ``` [⬆ back to top](#table-of-contents) @@ -1420,7 +1619,10 @@ Use `Array.reduce()` to add values into the array, using the sum of the last two ```js 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] +``` + +```js +factorial(6) -> 720 ``` [⬆ back to top](#table-of-contents) @@ -1433,8 +1635,11 @@ Use a mathematical formula to calculate the number of fibonacci numbers until `n ```js 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)); +``` + +```js +fibonacciCountUntilNum(10) -> 7 ``` [⬆ back to top](#table-of-contents) @@ -1451,8 +1656,11 @@ 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] +} +``` + +```js +fibonacciCountUntilNum(10) -> 7 ``` [⬆ back to top](#table-of-contents) @@ -1467,7 +1675,10 @@ Otherwise, return the GCD of `y` and the remainder of the division `x/y`. ```js const gcd = (x, y) => !y ? x : gcd(y, x % y); -// gcd (8, 36) -> 4 +``` + +```js +gcd (8, 36) -> 4 ``` [⬆ back to top](#table-of-contents) @@ -1482,27 +1693,33 @@ Count and return the number of `1`s in the string, using `match(/1/g)`. ```js const hammingDistance = (num1, num2) => ((num1 ^ num2).toString(2).match(/1/g) || '').length; -// hammingDistance(2,3) -> 1 +``` + +```js +hammingDistance(2,3) -> 1 ``` [⬆ back to top](#table-of-contents) ### inRange -Checks if the given number falls within the given range. +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`. ```js -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 true +inRange(3, 4) -> true +inRange(2, 3, 5) -> false +inrange(3, 2) -> false ``` [⬆ back to top](#table-of-contents) @@ -1515,10 +1732,13 @@ Convert the given number into an array of digits. Use `Math.pow()` to get the ap ```js 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( '' ) ); +``` + +```js +isArmstrongNumber(1634) -> true +isArmstrongNumber(371) -> true +isArmstrongNumber(56) -> false ``` [⬆ back to top](#table-of-contents) @@ -1531,7 +1751,10 @@ Use the modulo operator (`%`) to check if the remainder is equal to `0`. ```js const isDivisible = (dividend, divisor) => dividend % divisor === 0; -// isDivisible(6,3) -> true +``` + +```js +isDivisible(6,3) -> true ``` [⬆ back to top](#table-of-contents) @@ -1545,7 +1768,10 @@ Returns `true` if the number is even, `false` if the number is odd. ```js const isEven = num => num % 2 === 0; -// isEven(3) -> false +``` + +```js +isEven(3) -> false ``` [⬆ back to top](#table-of-contents) @@ -1554,7 +1780,7 @@ const isEven = num => num % 2 === 0; Checks if the provided integer is a prime number. -Check numbers from `2` to the square root of the given 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`. ```js @@ -1563,8 +1789,11 @@ const isPrime = num => { for (var i = 2; i * i <= boundary; i++) if (num % i == 0) return false; return num >= 2; }; -// isPrime(11) -> true -// isPrime(12) -> false +``` + +```js +isPrime(11) -> true +isPrime(12) -> false ``` [⬆ back to top](#table-of-contents) @@ -1581,7 +1810,10 @@ const lcm = (x, y) => { const gcd = (x, y) => !y ? x : gcd(y, x % y); return Math.abs(x * y) / (gcd(x, y)); }; -// lcm(12,7) -> 84 +``` + +```js +lcm(12,7) -> 84 ``` [⬆ back to top](#table-of-contents) @@ -1598,8 +1830,11 @@ 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 -// median([0,10,-2,7]) -> 3.5 +``` + +```js +median([5,6,50,1,-5]) -> 5 +median([0,10,-2,7]) -> 3.5 ``` [⬆ back to top](#table-of-contents) @@ -1616,8 +1851,11 @@ const palindrome = str => { const s = str.toLowerCase().replace(/[\W_]/g,''); return s === s.split('').reverse().join(''); } -// palindrome('taco cat') -> true - ``` +``` + +```js +palindrome('taco cat') -> true +``` [⬆ back to top](#table-of-contents) @@ -1630,8 +1868,11 @@ Use `Array.reduce()` to calculate how many numbers are below the value and how m ```js 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 - ``` +``` + +```js +percentile([1,2,3,4,5,6,7,8,9,10], 6) -> 55 +``` [⬆ back to top](#table-of-contents) @@ -1644,12 +1885,15 @@ Use `Array.reduce()` combined with `Array.map()` to iterate over elements and co ```js const powerset = arr => arr.reduce((a, v) => a.concat(a.map(r => [v].concat(r))), [[]]); -// powerset([1,2]) -> [[], [1], [2], [2,1]] +``` + +```js +powerset([1,2]) -> [[], [1], [2], [2,1]] ``` [⬆ back to top](#table-of-contents) -### primes +### primes Generates primes up to a given number, using the Sieve of Eratosthenes. @@ -1657,13 +1901,16 @@ Generate an array from `2` to the given number. Use `Array.filter()` to filter o ```js 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] +} +``` + +```js +primes(10) -> [2,3,5,7] ``` [⬆ back to top](#table-of-contents) @@ -1676,7 +1923,10 @@ Use `Math.random()` to generate a random number and map it to the desired range, ```js const randomIntegerInRange = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min; -// randomIntegerInRange(0, 5) -> 2 +``` + +```js +randomIntegerInRange(0, 5) -> 2 ``` [⬆ back to top](#table-of-contents) @@ -1689,7 +1939,10 @@ Use `Math.random()` to generate a random value, map it to the desired range usin ```js const randomNumberInRange = (min, max) => Math.random() * (max - min) + min; -// randomNumberInRange(2,10) -> 6.0211363285087005 +``` + +```js +randomNumberInRange(2,10) -> 6.0211363285087005 ``` [⬆ back to top](#table-of-contents) @@ -1702,8 +1955,11 @@ Use `Math.round()` and template literals to round the number to the specified nu Omit the second argument, `decimals` to round to an integer. ```js -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}`); +``` + +```js +round(1.005, 2) -> 1.01 ``` [⬆ back to top](#table-of-contents) @@ -1743,8 +1999,11 @@ const standardDeviation = (arr, usePopulation = false) => { .reduce((acc, val) => acc + val, 0) / (arr.length - (usePopulation ? 0 : 1)) ); }; -// standardDeviation([10,2,38,23,38,23,21]) -> 13.284434142114991 (sample) -// standardDeviation([10,2,38,23,38,23,21], true) -> 12.29899614287479 (population) +``` + +```js +standardDeviation([10,2,38,23,38,23,21]) -> 13.284434142114991 (sample) +standardDeviation([10,2,38,23,38,23,21], true) -> 12.29899614287479 (population) ``` [⬆ back to top](#table-of-contents) @@ -1765,7 +2024,10 @@ const speechSynthesis = message => { msg.voice = window.speechSynthesis.getVoices()[0]; window.speechSynthesis.speak(msg); }; -// speechSynthesis('Hello, World') -> plays the message +``` + +```js +speechSynthesis('Hello, World') -> // plays the message ``` [⬆ back to top](#table-of-contents) @@ -1779,8 +2041,11 @@ Use `fs.writeFile()`, template literals and `JSON.stringify()` to write a `json` ```js 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)) +``` + +```js +JSONToFile({test: "is passed"}, 'testJsonFile') -> writes the object to 'testJsonFile.json' ``` [⬆ back to top](#table-of-contents) @@ -1795,16 +2060,17 @@ creating an array from contents of file by `split`ing file content line by line ```js 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'); +``` + +```js +contents of test.txt : + line1 + line2 + line3 + ___________________________ +let arr = readFileLines('test.txt') +console.log(arr) // -> ['line1', 'line2', 'line3'] ``` [⬆ back to top](#table-of-contents) @@ -1825,13 +2091,14 @@ const cleanObj = (obj, keysToKeep = [], childIndicator) => { } else if (!keysToKeep.includes(key)) { delete obj[key]; } -  }); - return obj; -}; -/* - const testObj = {a: 1, b: 2, children: {a: 1, b: 2}} - cleanObj(testObj, ["a"],"children") // { a: 1, children : { a: 1}} -*/ + }) +} +``` + +```js +const testObj = {a: 1, b: 2, children: {a: 1, b: 2}} +cleanObj(testObj, ["a"],"children") +console.log(testObj) // { a: 1, children : { a: 1}} ``` [⬆ back to top](#table-of-contents) @@ -1844,7 +2111,10 @@ Use `Array.reduce()` to create and combine key-value pairs. ```js const objectFromPairs = arr => arr.reduce((a, v) => (a[v[0]] = v[1], a), {}); -// objectFromPairs([['a',1],['b',2]]) -> {a: 1, b: 2} +``` + +```js +objectFromPairs([['a',1],['b',2]]) -> {a: 1, b: 2} ``` [⬆ back to top](#table-of-contents) @@ -1857,7 +2127,10 @@ Use `Object.keys()` and `Array.map()` to iterate over the object's keys and prod ```js const objectToPairs = obj => Object.keys(obj).map(k => [k, obj[k]]); -// objectToPairs({a: 1, b: 2}) -> [['a',1],['b',2]]) +``` + +```js +objectToPairs({a: 1, b: 2}) -> [['a',1],['b',2]]) ``` [⬆ back to top](#table-of-contents) @@ -1880,12 +2153,13 @@ const orderBy = (arr, props, orders) => return acc; }, 0) ); -/* +``` + +```js 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}] -*/ ``` [⬆ back to top](#table-of-contents) @@ -1899,9 +2173,11 @@ If the property does not exists returns `undefined`. ```js 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' +```js +const obj = {selector: {to: {val: 'val to select'}}}; +select(obj, 'selector.to.val'); -> 'val to select' ``` [⬆ back to top](#table-of-contents) @@ -1914,11 +2190,12 @@ Use `Object.assign()` and an empty object (`{}`) to create a shallow clone of th ```js const shallowClone = obj => Object.assign({}, obj); -/* +``` + +```js const a = { x: true, y: 1 }; const b = shallowClone(a); a === b -> false -*/ ``` [⬆ back to top](#table-of-contents) @@ -1928,10 +2205,13 @@ 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. - + ```js const truthCheckCollection = (collection, pre) => (collection.every(obj => obj[pre])); -// truthCheckCollection([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}], "sex") -> true +``` + +```js +truthCheckCollection([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}], "sex") -> true ``` [⬆ back to top](#table-of-contents) @@ -1952,7 +2232,10 @@ const anagrams = str => { 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'] +``` + +```js +anagrams('abc') -> ['abc','acb','bac','bca','cab','cba'] ``` [⬆ back to top](#table-of-contents) @@ -1967,8 +2250,11 @@ Omit the `lowerRest` parameter to keep the rest of the string intact, or set it ```js const capitalize = ([first, ...rest], lowerRest = false) => first.toUpperCase() + (lowerRest ? rest.join('').toLowerCase() : rest.join('')); -// capitalize('myName') -> 'MyName' -// capitalize('myName', true) -> 'Myname' +``` + +```js +capitalize('fooBar') -> 'FooBar' +capitalize('fooBar', true) -> 'Foobar' ``` [⬆ back to top](#table-of-contents) @@ -1981,7 +2267,10 @@ Use `replace()` to match the first character of each word and `toUpperCase()` to ```js const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase()); -// capitalizeEveryWord('hello world!') -> 'Hello World!' +``` + +```js +capitalizeEveryWord('hello world!') -> 'Hello World!' ``` [⬆ back to top](#table-of-contents) @@ -1994,8 +2283,11 @@ Use a regular expression to count the number of vowels `(A, E, I, O, U)` in a `s ```js const countVowels = str => (str.match(/[aeiou]/ig) || []).length; -// countVowels('foobar') -> 3 -// countVowels('gym') -> 0 +``` + +```js +countVowels('foobar') -> 3 +countVowels('gym') -> 0 ``` [⬆ back to top](#table-of-contents) @@ -2008,7 +2300,10 @@ Use `replace()` to escape special characters. ```js const escapeRegExp = str => str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); -// escapeRegExp('(test)') -> \\(test\\) +``` + +```js +escapeRegExp('(test)') -> \\(test\\) ``` [⬆ back to top](#table-of-contents) @@ -2024,9 +2319,12 @@ 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' +``` + +```js +fromCamelCase('someDatabaseFieldName', ' ') -> 'some database field name' +fromCamelCase('someLabelThatNeedsToBeCamelized', '-') -> 'some-label-that-needs-to-be-camelized' +fromCamelCase('someJavascriptProperty', '_') -> 'some_javascript_property' ``` [⬆ back to top](#table-of-contents) @@ -2038,11 +2336,14 @@ Repeats a string n times using `String.repeat()` If no string is provided the default is `""` and the default number of times is 2. ```js -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; +} +``` + +```js +repeatString("abc",3) -> 'abcabcabc' +repeatString("abc") -> 'abcabc' ``` [⬆ back to top](#table-of-contents) @@ -2056,7 +2357,10 @@ Combine characters to get a string using `join('')`. ```js const reverseString = str => str.split('').reverse().join(''); -// reverseString('foobar') -> 'raboof' +``` + +```js +reverseString('foobar') -> 'raboof' ``` [⬆ back to top](#table-of-contents) @@ -2070,7 +2374,10 @@ Split the string using `split('')`, `Array.sort()` utilizing `localeCompare()`, ```js const sortCharactersInString = str => str.split('').sort((a, b) => a.localeCompare(b)).join(''); -// sortCharactersInString('cabbage') -> 'aabbceg' +``` + +```js +sortCharactersInString('cabbage') -> 'aabbceg' ``` [⬆ back to top](#table-of-contents) @@ -2087,12 +2394,15 @@ const toCamelCase = str => { let s = str && str.match(/[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g) .map(x => x.slice(0, 1).toUpperCase() + x.slice(1).toLowerCase()) .join(''); - return s.slice(0, 1).toLowerCase() + s.slice(1); -}; -// 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' + return s.slice(0,1).toLowerCase() + s.slice(1) + } +``` + +```js +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' ``` [⬆ back to top](#table-of-contents) @@ -2109,11 +2419,14 @@ 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) .map(x => x.toLowerCase()) .join('-'); -// 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" +``` + +```js +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" ``` [⬆ back to top](#table-of-contents) @@ -2130,13 +2443,15 @@ 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) .map(x => x.toLowerCase()) .join('_'); -}; -// 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_small_things" -// toSnakeCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML') -> "i_am_listening_to_fm_while_loading_different_url_on_my_browser_and_also_editing_some_xml_and_html" +``` + +```js +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" ``` [⬆ back to top](#table-of-contents) @@ -2151,7 +2466,10 @@ Return the string truncated to the desired length, with `...` appended to the en ```js const truncateString = (str, num) => str.length > num ? str.slice(0, num > 3 ? num - 3 : num) + '...' : str; -// truncateString('boomerang', 7) -> 'boom...' +``` + +```js +truncateString('boomerang', 7) -> 'boom...' ``` [⬆ back to top](#table-of-contents) @@ -2165,8 +2483,11 @@ Omit the second argument to use the default regex. ```js 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"] +``` + +```js +words("I love javaScript!!") -> ["I", "love", "javaScript"] +words("python, javaScript & coffee") -> ["python", "javaScript", "coffee"] ``` [⬆ back to top](#table-of-contents) @@ -2179,8 +2500,11 @@ Returns the first non-null/undefined argument. Use `Array.find()` to return the first non `null`/`undefined` argument. ```js -const coalesce = (...args) => args.find(_ => ![undefined, null].includes(_)); -// coalesce(null,undefined,"",NaN, "Waldo") -> "" +const coalesce = (...args) => args.find(_ => ![undefined, null].includes(_)) +``` + +```js +coalesce(null,undefined,"",NaN, "Waldo") -> "" ``` [⬆ back to top](#table-of-contents) @@ -2193,8 +2517,11 @@ Use `Array.find()` to return the first argument that returns `true` from the pro ```js const coalesceFactory = valid => (...args) => args.find(valid); -// const customCoalesce = coalesceFactory(_ => ![null, undefined, "", NaN].includes(_)) -// customCoalesce(undefined, null, NaN, "", "Waldo") //-> "Waldo" +``` + +```js +const customCoalesce = coalesceFactory(_ => ![null, undefined, "", NaN].includes(_)) +customCoalesce(undefined, null, NaN, "", "Waldo") // "Waldo" ``` [⬆ back to top](#table-of-contents) @@ -2207,9 +2534,12 @@ Use `Array.map()`, `split()` and `Array.join()` to join the mapped array for con `String.slice()` is used to remove `#` from string start since it's added once. ```js 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('') +``` + +```js +extendHex('#03f') -> '#0033ff' +extendHex('05a') -> '#0055aa' ``` [⬆ back to top](#table-of-contents) @@ -2223,7 +2553,10 @@ Returns lowercased constructor name of value, "undefined" or "null" if value is ```js const getType = v => v === undefined ? 'undefined' : v === null ? 'null' : v.constructor.name.toLowerCase(); -// getType(new Set([1,2,3])) -> "set" +``` + +```js +getType(new Set([1,2,3])) -> "set" ``` [⬆ back to top](#table-of-contents) @@ -2246,9 +2579,12 @@ const hexToRGB = hex => { ((h & (alpha ? 0x0000ff00 : 0x0000ff)) >>> (alpha ? 8 : 0)) + (alpha ? `, ${(h & 0x000000ff)}` : '') + ')'; }; -// hexToRGB('#27ae60ff') -> 'rgba(39, 174, 96, 255)' -// hexToRGB('27ae60') -> 'rgb(39, 174, 96)' -// hexToRGB('#fff') -> 'rgb(255, 255, 255)' +``` + +```js +hexToRGB('#27ae60ff') -> 'rgba(39, 174, 96, 255)' +hexToRGB('27ae60') -> 'rgb(39, 174, 96)' +hexToRGB('#fff') -> 'rgb(255, 255, 255)' ``` [⬆ back to top](#table-of-contents) @@ -2261,8 +2597,11 @@ Use `Array.isArray()` to check if a value is classified as an array. ```js const isArray = val => !!val && Array.isArray(val); -// isArray(null) -> false -// isArray([1]) -> true +``` + +```js +isArray(null) -> false +isArray([1]) -> true ``` [⬆ back to top](#table-of-contents) @@ -2275,8 +2614,11 @@ Use `typeof` to check if a value is classified as a boolean primitive. ```js const isBoolean = val => typeof val === 'boolean'; -// isBoolean(null) -> false -// isBoolean(false) -> true +``` + +```js +isBoolean(null) -> false +isBoolean(false) -> true ``` [⬆ back to top](#table-of-contents) @@ -2289,8 +2631,11 @@ Use `typeof` to check if a value is classified as a function primitive. ```js const isFunction = val => val && typeof val === 'function'; -// isFunction('x') -> false -// isFunction(x => x) -> true +``` + +```js +isFunction('x') -> false +isFunction(x => x) -> true ``` [⬆ back to top](#table-of-contents) @@ -2303,10 +2648,12 @@ Use `typeof` to check if a value is classified as a number primitive. ```js const isNumber = val => typeof val === 'number'; -// isNumber('1') -> false -// isNumber(1) -> true ``` +```js +isNumber('1') -> false +isNumber(1) -> true +``` [⬆ back to top](#table-of-contents) ### isString @@ -2317,8 +2664,11 @@ Use `typeof` to check if a value is classified as a string primitive. ```js const isString = val => typeof val === 'string'; -// isString(10) -> false -// isString('10') -> true +``` + +```js +isString(10) -> false +isString('10') -> true ``` [⬆ back to top](#table-of-contents) @@ -2331,8 +2681,11 @@ Use `typeof` to check if a value is classified as a symbol primitive. ```js const isSymbol = val => typeof val === 'symbol'; -// isSymbol('x') -> false -// isSymbol(Symbol('x')) -> true +``` + +```js +isSymbol('x') -> false +isSymbol(Symbol('x')) -> true ``` [⬆ back to top](#table-of-contents) @@ -2341,17 +2694,16 @@ const isSymbol = val => typeof val === 'symbol'; 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)`. +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)`. ```js -const randomHexColor = () => { - let n = (Math.random() * 0xfffff | 0).toString(16); - return '#' + (n.length !== 6 - ? (Math.random() * 0xf | 0).toString(16) + n : n); -}; -// randomHexColorCode() -> "#e34155" -// randomHexColorCode() -> "#fd73a6" -// randomHexColorCode() -> "#4144c6" +const randomHexColorCode = () => '#'+(Math.random()*0xFFFFFF<<0).toString(16); +``` + +```js +randomHexColorCode() -> "#e34155" +randomHexColorCode() -> "#fd73a6" +randomHexColorCode() -> "#4144c6" ``` [⬆ back to top](#table-of-contents) @@ -2364,7 +2716,10 @@ Convert given RGB parameters to hexadecimal string using bitwise left-shift oper ```js const RGBToHex = (r, g, b) => ((r << 16) + (g << 8) + b).toString(16).padStart(6, '0'); -// RGBToHex(255, 165, 1) -> 'ffa501' +``` + +```js +RGBToHex(255, 165, 1) -> 'ffa501' ``` [⬆ back to top](#table-of-contents) @@ -2380,8 +2735,11 @@ const timeTaken = callback => { console.time('timeTaken'); const r = callback(); console.timeEnd('timeTaken'); return r; }; -// timeTaken(() => Math.pow(2, 10)) -> 1024 -// (logged): timeTaken: 0.02099609375ms +``` + +```js +timeTaken(() => Math.pow(2, 10)) -> 1024 +(logged): timeTaken: 0.02099609375ms ``` [⬆ back to top](#table-of-contents) @@ -2391,8 +2749,11 @@ const timeTaken = callback => { Use `toLocaleString()` to convert a float-point arithmetic to the [Decimal mark](https://en.wikipedia.org/wiki/Decimal_mark) form. It makes a comma separated string from a number. ```js -const toDecimalMark = num => num.toLocaleString('en-US'); -// toDecimalMark(12305030388.9087) -> "12,305,030,388.9087" +const toDecimalMark = num => num.toLocaleString("en-US"); +``` + +```js +toDecimalMark(12305030388.9087) -> "12,305,030,388.9087" ``` [⬆ back to top](#table-of-contents) @@ -2412,7 +2773,10 @@ const toOrdinalSuffix = num => { 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" +``` + +```js +toOrdinalSuffix("123") -> "123rd" ``` [⬆ back to top](#table-of-contents) @@ -2428,7 +2792,10 @@ const UUIDGenerator = () => ([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' +``` + +```js +UUIDGenerator() -> '7982fcfe-5721-4632-bede-6000885be57d' ``` [⬆ back to top](#table-of-contents) @@ -2443,7 +2810,10 @@ Use `Number()` to check if the coercion holds. ```js const validateNumber = n => !isNaN(parseFloat(n)) && isFinite(n) && Number(n) == n; -// validateNumber('10') -> true +``` + +```js +validateNumber('10') -> true ``` [⬆ back to top](#table-of-contents) @@ -2451,4 +2821,3 @@ const validateNumber = n => !isNaN(parseFloat(n)) && isFinite(n) && Number(n) == ## Credits *Icons made by [Smashicons](https://www.flaticon.com/authors/smashicons) from [www.flaticon.com](https://www.flaticon.com/) is licensed by [CC 3.0 BY](http://creativecommons.org/licenses/by/3.0/).* -