1、all

const all = (arr, fn = Boolean) => arr.every(fn);
all([4, 2, 3], x => x > 1); // trueall([1, 2, 3]); // true

2、allEqual

const allEqual = arr => arr.every(val => val === arr[0]);
allEqual([1, 2, 3, 4, 5, 6]); // falseallEqual([1, 1, 1, 1]); // true

3、approximatelyEqual

const approximatelyEqual = (v1, v2, epsilon = 0.001) => Math.abs(v1 - v2) < epsilon;
approximatelyEqual(Math.PI / 2.0, 1.5708); // true

4、arrayToCSV

const arrayToCSV = (arr, delimiter = ',') =>  arr.map(v => v.map(x => `"${x}"`).join(delimiter)).join('\n');  arrayToCSV([['a', 'b'], ['c', 'd']]); // '"a","b"\n"c","d"'arrayToCSV([['a', 'b'], ['c', 'd']], ';'); // '"a";"b"\n"c";"d"'

5、arrayToHtmlList

const arrayToHtmlList = (arr, listID) =>  (el => (    (el = document.querySelector('#' + listID)),    (el.innerHTML += arr.map(item => `<li>${item}</li>`).join(''))  ))();  arrayToHtmlList(['item 1', 'item 2'], 'myListID');

6、attempt

const attempt = (fn, ...args) => {  try {    return fn(...args);  } catch (e) {    return e instanceof Error ? e : new Error(e);  }};var elements = attempt(function(selector) {  return document.querySelectorAll(selector);}, '>_>');if (elements instanceof Error) elements = []; // elements = []

7、average

const average = (...nums) => nums.reduce((acc, val) => acc + val, 0) / nums.length;average(...[1, 2, 3]); // 2average(1, 2, 3); // 2

8、averageBy

const averageBy = (arr, fn) =>  arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => acc + val, 0) /  arr.length;  averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 5averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 5

9、bifurcate

const bifurcate = (arr, filter) =>  arr.reduce((acc, val, i) => (acc[filter[i] ? 0 : 1].push(val), acc), [[], []]);bifurcate(['beep', 'boop', 'foo', 'bar'], [true, true, false, true]);// [ ['beep', 'boop', 'bar'], ['foo'] ]

10、bifurcateBy

const bifurcateBy = (arr, fn) =>  arr.reduce((acc, val, i) => (acc[fn(val, i) ? 0 : 1].push(val), acc), [[], []]);  bifurcateBy(['beep', 'boop', 'foo', 'bar'], x => x[0] === 'b');// [ ['beep', 'boop', 'bar'], ['foo'] ]

11、bottomVisible

const bottomVisible = () =>  document.documentElement.clientHeight + window.scrollY >=  (document.documentElement.scrollHeight || document.documentElement.clientHeight);
bottomVisible(); // true

12、byteSize

const byteSize = str => new Blob([str]).size;
byteSize('😀'); // 4byteSize('Hello World'); // 11

13、capitalize

const capitalize = ([first, ...rest]) =>  first.toUpperCase() + rest.join('');  capitalize('fooBar'); // 'FooBar'capitalize('fooBar', true); // 'FooBar'

14、capitalizeEveryWord

const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());
capitalizeEveryWord('hello world!'); // 'Hello World!'

15、castArray

const castArray = val => (Array.isArray(val) ? val : [val]);
castArray('foo'); // ['foo']castArray([1]); // [1]

16、compact

const compact = arr => arr.filter(Boolean);
compact([0, 1, false, 2, '', 3, 'a', 'e' * 23, NaN, 's', 34]);// [ 1, 2, 3, 'a', 's', 34 ]

17、countOccurrences

const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);countOccurrences([1, 1, 2, 1, 2, 3], 1); // 3

18、Create Directory

const fs = require('fs');const createDirIfNotExists = dir => (!fs.existsSync(dir) ? fs.mkdirSync(dir) : undefined);createDirIfNotExists('test');// creates the directory 'test', if it doesn't exist

19、currentURL

const currentURL = () => window.location.href;
currentURL(); // 'https://medium.com/@fatosmorina'

20、dayOfYear

const dayOfYear = date =>  Math.floor((date - new Date(date.getFullYear(), 0, 0)) / 1000 / 60 / 60 / 24);
dayOfYear(new Date()); // 272

21、decapitalize

const decapitalize = ([first, ...rest]) =>  first.toLowerCase() + rest.join('')
decapitalize('FooBar'); // 'fooBar'

22、deepFlatten

const deepFlatten = arr => [].concat(...arr.map(v => (Array.isArray(v) ? deepFlatten(v) : v)));
deepFlatten([1, [2], [[3], 4], 5]); // [1,2,3,4,5]

23、default

const defaults = (obj, ...defs) => Object.assign({}, obj, ...defs.reverse(), obj);
defaults({ a: 1 }, { b: 2 }, { b: 6 }, { a: 3 }); // { a: 1, b: 2 }

24、defer

const defer = (fn, ...args) => setTimeout(fn, 1, ...args);
defer(console.log, 'a'), console.log('b'); // logs 'b' then 'a'

25、degreesToRads

const degreesToRads = deg => (deg * Math.PI) / 180.0;
degreesToRads(90.0); // ~1.5708

26、difference

const difference = (a, b) => {  const s = new Set(b);  return a.filter(x => !s.has(x));};
difference([1, 2, 3], [1, 2, 4]); // [3]

27、differenceBy

const differenceBy = (a, b, fn) => {  const s = new Set(b.map(fn));  return a.filter(x => !s.has(fn(x)));};
differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1.2]differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [ { x: 2 } ]

28、differenceWith

const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
differenceWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0], (a, b) => Math.round(a) === Math.round(b));// [1, 1.2]

29、digitize

const digitize = n => [...`${n}`].map(i => parseInt(i));
digitize(431); // [4, 3, 1]

30、distance

const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0);
distance(1, 1, 2, 3); // 2.23606797749979

31、drop

const drop = (arr, n = 1) => arr.slice(n);
drop([1, 2, 3]); // [2,3]drop([1, 2, 3], 2); // [3]drop([1, 2, 3], 42); // []

32、dropRight

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); // []

33、dropRightWhile

const dropRightWhile = (arr, func) => {  while (arr.length > 0 && !func(arr[arr.length - 1])) arr = arr.slice(0, -1);  return arr;};
dropRightWhile([1, 2, 3, 4], n => n < 3); // [1, 2]

34、dropWhile

const dropWhile = (arr, func) => {  while (arr.length > 0 && !func(arr[0])) arr = arr.slice(1);  return arr;};
dropWhile([1, 2, 3, 4], n => n >= 3); // [3,4]

35、elementContains

const elementContains = (parent, child) => parent !== child && parent.contains(child);
elementContains(document.querySelector('head'), document.querySelector('title')); // trueelementContains(document.querySelector('body'), document.querySelector('body')); // false

36、filterNonUnique

const filterNonUnique = arr => [ …new Set(arr)];filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1, 2, 3, 4, 5]

37、findKey

const findKey = (obj, fn) => Object.keys(obj).find(key => fn(obj[key], key, obj));
findKey(  {    barney: { age: 36, active: true },    fred: { age: 40, active: false },    pebbles: { age: 1, active: true }  },  o => o['active']); // 'barney'

38、findLast

const findLast = (arr, fn) => arr.filter(fn).pop();
findLast([1, 2, 3, 4], n => n % 2 === 1); // 3

39、flatten

const flatten = (arr, depth = 1) =>  arr.reduce((a, v) => a.concat(depth > 1 && Array.isArray(v) ? flatten(v, depth - 1) : v), []);
flatten([1, [2], 3, 4]); // [1, 2, 3, 4]flatten([1, [2, [3, [4, 5], 6], 7], 8], 2); // [1, 2, 3, [4, 5], 6, 7, 8]

40、forEachRight

const forEachRight = (arr, callback) =>  arr    .slice(0)    .reverse()    .forEach(callback);    forEachRight([1, 2, 3, 4], val => console.log(val)); // '4', '3', '2', '1'

41、forOwn

const forOwn = (obj, fn) => Object.keys(obj).forEach(key => fn(obj[key], key, obj));forOwn({ foo: 'bar', a: 1 }, v => console.log(v)); // 'bar', 1

42、functionName

const functionName = fn => (console.debug(fn.name), fn);
functionName(Math.max); // max (logged in debug channel of console)

43、getColonTimeFromDate

const getColonTimeFromDate = date => date.toTimeString().slice(0, 8);getColonTimeFromDate(new Date()); // "08:38:00"

44、getDaysDiffBetweenDates

const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>  (dateFinal - dateInitial) / (1000 * 3600 * 24);  getDaysDiffBetweenDates(new Date('2019-01-13'), new Date('2019-01-15')); // 2

45、getStyle

const getStyle = (el, ruleName) => getComputedStyle(el)[ruleName];
getStyle(document.querySelector('p'), 'font-size'); // '16px'

46、getType

const getType = v =>  v === undefined ? 'undefined' : v === null ? 'null' : v.constructor.name.toLowerCase();  getType(new Set([1, 2, 3])); // 'set'

47、hasClass

const hasClass = (el, className) => el.classList.contains(className);hasClass(document.querySelector('p.special'), 'special'); // true

48、head

const head = arr => arr[0];
head([1, 2, 3]); // 1

49、hide

const hide = (...el) => [...el].forEach(e => (e.style.display = 'none'));
hide(document.querySelectorAll('img')); // Hides all <img> elements on the page

50、httpsRedirect

const httpsRedirect = () => {  if (location.protocol !== 'https:') location.replace('https://' + location.href.split('//')[1]);};
httpsRedirect(); // If you are on http://mydomain.com, you are redirected to https://mydomain.com

51、indexOfAll

const indexOfAll = (arr, val) => arr.reduce((acc, el, i) => (el === val ? [...acc, i] : acc), []);
indexOfAll([1, 2, 3, 1, 2, 3], 1); // [0,3]indexOfAll([1, 2, 3], 4); // []

52、initial

const initial = arr => arr.slice(0, -1);
initial([1, 2, 3]); // [1,2]const initial = arr => arr.slice(0, -1);initial([1, 2, 3]); // [1,2]

53、insertAfter

const insertAfter = (el, htmlString) => el.insertAdjacentHTML('afterend', htmlString);
insertAfter(document.getElementById('myId'), '<p>after</p>'); // <div id="myId">...</div> <p>after</p>

54、insertBefore

const insertBefore = (el, htmlString) => el.insertAdjacentHTML('beforebegin', htmlString);
insertBefore(document.getElementById('myId'), '<p>before</p>'); // <p>before</p> <div id="myId">...</div>

55、intersection

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]

56、intersectionBy

const intersectionBy = (a, b, fn) => {  const s = new Set(b.map(fn));  return a.filter(x => s.has(fn(x)));};
intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [2.1]

57、intersectionBy

const intersectionWith = (a, b, comp) => a.filter(x => b.findIndex(y => comp(x, y)) !== -1);
intersectionWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0, 3.9], (a, b) => Math.round(a) === Math.round(b)); // [1.5, 3, 0]

58、is

const is = (type, val) => ![, null].includes(val) && val.constructor === type;
is(Array, [1]); // trueis(ArrayBuffer, new ArrayBuffer()); // trueis(Map, new Map()); // trueis(RegExp, /./g); // trueis(Set, new Set()); // trueis(WeakMap, new WeakMap()); // trueis(WeakSet, new WeakSet()); // trueis(String, ''); // trueis(String, new String('')); // trueis(Number, 1); // trueis(Number, new Number(1)); // trueis(Boolean, true); // trueis(Boolean, new Boolean(true)); // true

59、isAfterDate

const isAfterDate = (dateA, dateB) => dateA > dateB;
isAfterDate(new Date(2010, 10, 21), new Date(2010, 10, 20)); // true

60、isAnagram

const isAnagram = (str1, str2) => {  const normalize = str =>    str      .toLowerCase()      .replace(/[^a-z0-9]/gi, '')      .split('')      .sort()      .join('');  return normalize(str1) === normalize(str2);};
isAnagram('iceman', 'cinema'); // true

61、isArrayLike

const isArrayLike = obj => obj != null && typeof obj[Symbol.iterator] === 'function';
isArrayLike(document.querySelectorAll('.className')); // trueisArrayLike('abc'); // trueisArrayLike(null); // false

62、isBeforeDate

const isBeforeDate = (dateA, dateB) => dateA < dateB;
isBeforeDate(new Date(2010, 10, 20), new Date(2010, 10, 21)); // true

63、isBoolean

const isBoolean = val => typeof val === 'boolean';isBoolean(null); // falseisBoolean(false); // true

64、getColonTimeFromDate

const isBrowser = () => ![typeof window, typeof document].includes('undefined');
isBrowser(); // true (browser)isBrowser(); // false (Node)

65、isBrowserTabFocused

const isBrowserTabFocused = () => !document.hidden;isBrowserTabFocused(); // true

66、isLowerCase

const isLowerCase = str => str === str.toLowerCase();
isLowerCase('abc'); // trueisLowerCase('a3@$'); // trueisLowerCase('Ab4'); // false

67、isNil

const isNil = val => val === undefined || val === null;
isNil(null); // trueisNil(undefined); // true

68、isNull

const isNull = val => val === null;
isNull(null); // true

69、isNumber

function isNumber(n) {    return !isNaN(parseFloat(n)) && isFinite(n);}
isNumber('1'); // falseisNumber(1); // true

70、isObject

const isObject = obj => obj === Object(obj);
isObject([1, 2, 3, 4]); // trueisObject([]); // trueisObject(['Hello!']); // trueisObject({ a: 1 }); // trueisObject({}); // trueisObject(true); // false

71、isObjectLike

const isObjectLike = val => val !== null && typeof val === 'object';
isObjectLike({}); // trueisObjectLike([1, 2, 3]); // trueisObjectLike(x => x); // falseisObjectLike(null); // false

72、isPlainObject

const isPlainObject = val => !!val && typeof val === 'object' && val.constructor === Object;
isPlainObject({ a: 1 }); // trueisPlainObject(new Map()); // false

73、isPromiseLike

const isPromiseLike = obj =>  obj !== null &&  (typeof obj === 'object' || typeof obj === 'function') &&  typeof obj.then === 'function';  isPromiseLike({  then: function() {    return '';  }}); // trueisPromiseLike(null); // falseisPromiseLike({}); // false

74、isSameDate

const isSameDate = (dateA, dateB) => dateA.toISOString() === dateB.toISOString();
isSameDate(new Date(2010, 10, 20), new Date(2010, 10, 20)); // true

75、isString

const isString = val => typeof val === 'string';
isString('10'); // true

76、isSymbol

const isSymbol = val => typeof val === 'symbol';
isSymbol(Symbol('x')); // true

77、isUndefined

const isUndefined = val => val === undefined;
isUndefined(undefined); // true

78、isUpperCase

const isUpperCase = str => str === str.toUpperCase();
isUpperCase('ABC'); // trueisLowerCase('A3@$'); // trueisLowerCase('aB4'); // false

79、isValidJSON

const isValidJSON = str => {  try {    JSON.parse(str);    return true;  } catch (e) {    return false;  }};
isValidJSON('{"name":"Adam","age":20}'); // trueisValidJSON('{"name":"Adam",age:"20"}'); // falseisValidJSON(null); // true

80、last

const last = arr => arr[arr.length - 1];
last([1, 2, 3]); // 3

81、matches

onst matches = (obj, source) =>  Object.keys(source).every(key => obj.hasOwnProperty(key) && obj[key] === source[key]);  matches({ age: 25, hair: 'long', beard: true }, { hair: 'long', beard: true }); // truematches({ hair: 'long', beard: true }, { age: 25, hair: 'long', beard: true }); // false

82、maxDate

const maxDate = (...dates) => new Date(Math.max.apply(null, ...dates));
const array = [  new Date(2017, 4, 13),  new Date(2018, 2, 12),  new Date(2016, 0, 10),  new Date(2016, 0, 9)];maxDate(array); // 2018-03-11T22:00:00.000Z

83、maxN

const maxN = (arr, n = 1) => [...arr].sort((a, b) => b - a).slice(0, n);
maxN([1, 2, 3]); // [3]maxN([1, 2, 3], 2); // [3,2]

84、minDate

const minDate = (...dates) => new Date(Math.min.apply(null, ...dates));
const array = [  new Date(2017, 4, 13),  new Date(2018, 2, 12),  new Date(2016, 0, 10),  new Date(2016, 0, 9)];minDate(array); // 2016-01-08T22:00:00.000Z