This article refers to the original text- http://bjbsair.com/2020-03-22/tech-info/2077/

JavaScript is currently one of the most popular programming languages, as most people say: "If you want to learn a programming language, learn JavaScript."

Quincy Larson, the founder of FreeCodeCamp, was asked in a recent interview which language developers should learn first.He replies, "JavaScript.":

You're not very excited to hear so much.Here are 127 common JS code snippets for you to learn and use.

1,all

Returns true if all elements of the array satisfy the function condition.When called, if the second parameter is omitted, the Boolean value is passed by default.

const all = (arr, fn = Boolean) => arr.every(fn);  

all([4, 2, 3], x => x > 1); // true  
all([1, 2, 3]); // true copy code

2,allEqual

Determine if the elements in the array are all equal

const allEqual = arr => arr.every(val => val === arr[0]);  

allEqual([1, 2, 3, 4, 5, 6]); // false  
allEqual([1, 1, 1, 1]); // true copy code

3,approximatelyEqual

This code sample checks whether two numbers are approximately equal, and the difference values can be set by passing parameters

const approximatelyEqual = (v1, v2, epsilon = 0.001) => Math.abs(v1 - v2) < epsilon;  

approximatelyEqual(Math.PI / 2.0, 1.5708); // true copy code

4,arrayToCSV

This code converts elements without commas or double quotes to strings with comma delimiters, which are recognized as CSV formats.

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''copy code

5,arrayToHtmlList

This code converts an array element into a <li>tag and adds this element to the given ID element tag.

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

arrayToHtmlList(['item 1', 'item 2'], 'myListID');Copy Code

6,attempt

This code executes a function, returns the remaining parameters back to the function as parameters, returns the corresponding results, and can catch exceptions.

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 = [] Copy Code

7,average

This code returns the average of two or more numbers.

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

8,averageBy

An example of a combination of the map() and reduce() functions that first converts objects into arrays through the map() function, then adds them up by calling the reduce() function, then returns the average based on the length of the array.

const averageBy = (arr, fn) =>  
  arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => acc + val, 0) /  
  arr.length;  

averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 5  
averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 5 Copy code

9,bifurcate

This function contains two parameters, each of which is an array. The array of one parameter is grouped according to the true or false condition of the second parameter, if it is placed in the first array and the other in the second.A combination of Array.prototype.reduce() and Array.prototype.push() is used here.

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']] Copy the code

10,bifurcateBy

This code groups the arrays according to the specified function logic. The logic that satisfies the function condition is true, and the other unsatisfactory arrays are placed in the second array.Array.prototype.reduce() is combined with Array.prototype.push(), which is added to the array through the Array.prototype.push() function based on the function filtering logic.

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']] Copy the code

11,bottomVisible

Used to detect whether a page scrolls to the bottom of the page.

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

bottomVisible(); // true copy code

12,byteSize

This code returns the byte length of the string.Blob objects are used here, and Blob (Binary Large Object) objects represent a piece of binary data and provide a series of operation interfaces.Other API s for manipulating binary data, such as File objects, are built on Blob objects and inherit their properties and methods.There are two ways to generate blob objects: one by using the Blob constructor and the other by slicing out a portion of an existing blob object.

const byteSize = str => new Blob([str]).size;  

byteSize(''); // 4  
byteSize('Hello World'); // 11 Copy code

13,capitalize

Converts the first letter of a string to uppercase, which mainly applies to the use of the ES6 expansion syntax in arrays.

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

capitalize('fooBar'); // 'FooBar'  
capitalize('fooBar', true); // 'FooBar'Copy Code

14,capitalizeEveryWord

Converts the first letter of each word in a sentence to uppercase, where regular expressions are used to replace it.

const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());  

capitalizeEveryWord('hello world!'); // 'Hello World!'Copy Code

15,castArray

This code converts a non-numeric value into an array object.

const castArray = val => (Array.isArray(val) ? val : [val]);  

castArray('foo'); // ['foo']  
castArray([1]); // [1] Copy code

16,compact

Remove the contents of the array that have a value of false.

const compact = arr => arr.filter(Boolean);  

compact([0, 1, false, 2, '', 3, 'a', 'e' * 23, NaN, 's', 34]);   
// [1, 2, 3,'a','s', 34] Copy code

17,countOccurrences

Count the number of occurrences of a value in an array

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

18,Create Directory

This snippet uses existSync() to check for the existence of a directory, and then uses mkdirSync() to create a directory if it does not exist.

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

19,currentURL

Returns the URL address currently accessed.

const currentURL = () => window.location.href;  

currentURL(); // 'https://medium.com/@fatosmorina'Copy Code

20,dayOfYear

Return to the current day of the year

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

dayOfYear(new Date()); // 272 Copy Code

21,decapitalize

Converts the first letter of a string to lowercase

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

decapitalize('FooBar'); // 'fooBar'

22,deepFlatten

Multidimensional arrays are flattened into one-dimensional arrays in a recursive form.

const deepFlatten = arr => [].concat(...arr.map(v => (Array.isArray(v) ? deepFlatten(v) : v)));  

deepFlatten([1, [2], [[3], 4], 5]); // Copy Code [1,2,3,4,5]

23,default

If the object contains duplicate attributes, the previous one will prevail.

const defaults = (obj, ...defs) => Object.assign({}, obj, ...defs.reverse(), obj);  

defaults({ a: 1 }, { b: 2 }, { b: 6 }, { a: 3 }); // {a: 1, b: 2} Copy Code

24,defer

Delay function call, that is, call function asynchronously.

const defer = (fn, ...args) => setTimeout(fn, 1, ...args);  

defer(console.log, 'a'), console.log('b'); // Logs'b'then'a' copy code

25,degreesToRads

This code converts standard degrees into radians.

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

degreesToRads(90.0); // ~1.5708 Copy Code

26,difference

This code looks for the difference between two given arrays and finds that the former array has no elements in the latter.

const difference = (a, b) => {  
  const s = new Set(b);  
  return a.filter(x => !s.has(x));  
};  

difference([1, 2, 3], [1, 2, 4]); // [3] Copy Code

27,differenceBy

Processing an array requiring comparison of differences through a given function finds that the former array has no elements in the latter.

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}] Copy Code

28,differenceWith

This code filters the arrays that need to be compared according to the given function logic to find out that the former array has no elements in the latter.

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));   
// Copy Code [1, 1.2]

29,digitize

Split the input number into an array of individual numbers.

const digitize = n => [...`${n}`].map(i => parseInt(i));  

digitize(431); // Copy Code [4, 3, 1]

30,distance

Calculate the distance between two points

const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0);  

distance(1, 1, 2, 3); // 2.23606797749979 Copy Code

31,drop

This code deletes n elements from the left of a given array

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); // [] Copy code

32,dropRight

This code deletes n elements from the right of a given array

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); // [] Copy code

33,dropRightWhile

This code deletes the given array from the right according to the given function condition until the current element meets the function condition True, stops deleting, and returns the remaining elements of the array.

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); // Copy Code [1, 2]

34,dropWhile

The array is filtered according to the given function conditions, and those that do not meet the function conditions are removed from the array.

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] Copy Code

35,elementContains

Receives two DOM element object parameters to determine if the latter is a child of the former.

const elementContains = (parent, child) => parent !== child && parent.contains(child);  

elementContains(document.querySelector('head'), document.querySelector('title')); // true  
elementContains(document.querySelector('body'), document.querySelector('body')); // false copy code

36,filterNonUnique

Remove duplicate elements from the array

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

37,findKey

Finds the key value of the first object that satisfies the given function condition.

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'copy code

38,findLast

Filter the array according to the given function condition, deleting the last element that meets the condition.

const findLast = (arr, fn) => arr.filter(fn).pop();  

findLast([1, 2, 3, 4], n => n % 2 === 1); // 3 Copy code

39,flatten

Flattens a nested array according to the depth of the specified array.

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] Copy Code

40,forEachRight

Executes in turn from the right to the left of the array according to the given function condition.

const forEachRight = (arr, callback) =>  
  arr  
    .slice(0)  
    .reverse()  
    .forEach(callback);  

forEachRight([1, 2, 3, 4], val => console.log(val)); // Copy Code'4','3','2','1'

41,forOwn

This code iterates over objects using three parameters as inputs (values, keys, objects themselves) according to a given function condition.

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 copy code

42,functionName

The name of this code output function.

const functionName = fn => (console.debug(fn.name), fn);  

functionName(Math.max); // max (logged in debug channel of console)

43,getColonTimeFromDate

This code gets the current time from the Date object.

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

44,getDaysDiffBetweenDates

This code returns the difference between two dates by how many days

const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>  
  (dateFinal - dateInitial) / (1000 * 3600 * 24);  

getDaysDiffBetweenDates(new Date('2019-01-13'), new Date('2019-01-15')); // 2 Copy code

45,getStyle

This code returns the attribute value corresponding to the DOM element node.

const getStyle = (el, ruleName) => getComputedStyle(el)[ruleName];  

getStyle(document.querySelector('p'), 'font-size'); // '16px'copy code

46,getType

The main function of this code is to return the type of data.

const getType = v =>  
  v === undefined ? 'undefined' : v === null ? 'null' : v.constructor.name.toLowerCase();  

getType(new Set([1, 2, 3])); // 'set'copy code

47,hasClass

This code returns whether the DOM element contains the specified Class style.

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

48,head

This code outputs the first element of the array.

const head = arr => arr[0];  

head([1, 2, 3]); // 1 Copy code

49,hide

This code hides the specified DOM element.

const hide = (...el) => [...el].forEach(e => (e.style.display = 'none'));  

hide(document.querySelectorAll('img')); // Hides all <img> elements on the page copy code

50,httpsRedirect

The function of this code is to redirect the http web address to the https web address.

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 Copy Code

51,indexOfAll

This code returns all index values corresponding to a value in the array, or an empty array if it is not included.

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); // [] Copy code

52,initial

This code returns all elements of the array except the last element

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] Copy Code

53,insertAfter

The main function of this code is to insert new node content after a given DOM node

const insertAfter = (el, htmlString) => el.insertAdjacentHTML('afterend', htmlString);  

insertAfter(document.getElementById('myId'), '<p>after</p>'); // <div id="myId">...</div> <p>after</p>Copy code

54,insertBefore

The main function of this code is to insert new node content before a given DOM node

const insertBefore = (el, htmlString) => el.insertAdjacentHTML('beforebegin', htmlString);  

insertBefore(document.getElementById('myId'), '<p>before</p>'); // <p>before</p> <div id="myId"> </div>Copy code

55,intersection

This code returns the intersection between two array elements.

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] Copy Code

56,intersectionBy

Processes the array elements that need to be compared according to the given function, then finds the intersection based on the processed array, and outputs the corresponding elements from the first array.

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] Copy Code

57,intersectionBy

Compare the differences between the two arrays according to the given function, find the intersection, and output the corresponding elements from the first array.

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)); // Copy Code [1.5, 3, 0]

58,is

This code is used to determine if the data is of the specified data type and returns true if it is.

const is = (type, val) => ![, null].includes(val) && val.constructor === type;  

is(Array, [1]); // true  
is(ArrayBuffer, new ArrayBuffer()); // true  
is(Map, new Map()); // true  
is(RegExp, /./g); // true  
is(Set, new Set()); // true  
is(WeakMap, new WeakMap()); // true  
is(WeakSet, new WeakSet()); // true  
is(String, ''); // true  
is(String, new String('')); // true  
is(Number, 1); // true  
is(Number, new Number(1)); // true  
is(Boolean, true); // true  
is(Boolean, new Boolean(true)); // true copy code

59,isAfterDate

Receives parameters of two date types to determine whether the former date is later than the latter.

const isAfterDate = (dateA, dateB) => dateA > dateB;  

isAfterDate(new Date(2010, 10, 21), new Date(2010, 10, 20)); // true copy code

60,isAnagram

Used to detect whether two words are similar.

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 copy code

61,isArrayLike

This code detects if the object is a class array object and is iterative.

const isArrayLike = obj => obj != null && typeof obj[Symbol.iterator] === 'function';  

isArrayLike(document.querySelectorAll('.className')); // true  
isArrayLike('abc'); // true  
isArrayLike(null); // false copy code

62,isBeforeDate

Receives parameters of two date types to determine whether the former date is earlier than the latter.

const isBeforeDate = (dateA, dateB) => dateA < dateB;  

isBeforeDate(new Date(2010, 10, 20), new Date(2010, 10, 21)); // true copy code

63,isBoolean

This code checks to see if the parameter is of Boolean type.

const isBoolean = val => typeof val === 'boolean';  

isBoolean(null); // false  
isBoolean(false); // true

64,getColonTimeFromDate

Used to determine if the program runs in a browser environment, which helps avoid errors when running front-end modules in a node environment.

const isBrowser = () => ![typeof window, typeof document].includes('undefined');  

isBrowser(); // true (browser)  
isBrowser(); // false (Node) copy code

65,isBrowserTabFocused

Used to determine if the current page is active (display).

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

66,isLowerCase

Used to determine if the current string is all lowercase.

const isLowerCase = str => str === str.toLowerCase();  

isLowerCase('abc'); // true  
isLowerCase('a3@$'); // true  
isLowerCase('Ab4'); // false copy code

67,isNil

Used to determine if the value of the current variable is null or undefined.

const isNil = val => val === undefined || val === null;  

isNil(null); // true  
isNil(undefined); // true copy code

68,isNull

Used to determine if the value of the current variable is null type.

const isNull = val => val === null;  

isNull(null); // true copy code

69,isNumber

Used to check if the current value is of numeric type.

function isNumber(n) {  
    return !isNaN(parseFloat(n)) && isFinite(n);  
}  

isNumber('1'); // false  
isNumber(1); // true copy code

70,isObject

To determine whether the value of a parameter is an object, an Object constructor is used to create an object wrapper that returns the original value if it is an object type.

const isObject = obj => obj === Object(obj);  

isObject([1, 2, 3, 4]); // true  
isObject([]); // true  
isObject(['Hello!']); // true  
isObject({ a: 1 }); // true  
isObject({}); // true  
isObject(true); // false copy code

71,isObjectLike

Used to check whether the value of a parameter is null and the type is an object.

const isObjectLike = val => val !== null && typeof val === 'object';  

isObjectLike({}); // true  
isObjectLike([1, 2, 3]); // true  
isObjectLike(x => x); // false  
isObjectLike(null); // false copy code

72,isPlainObject

This snippet checks whether the value of a parameter is an object created by an Object constructor.

const isPlainObject = val => !!val && typeof val === 'object' && val.constructor === Object;  

isPlainObject({ a: 1 }); // true  
isPlainObject(new Map()); // false copy code

73,isPromiseLike

Used to check if the current object resembles a Promise function.

const isPromiseLike = obj =>  
  obj !== null &&  
  (typeof obj === 'object' || typeof obj === 'function') &&  
  typeof obj.then === 'function';  

isPromiseLike({  
  then: function() {  
    return '';  
  }  
}); // true  
isPromiseLike(null); // false  
isPromiseLike({}); // false copy code

74,isSameDate

Used to determine whether two given dates are the same day.

const isSameDate = (dateA, dateB) => dateA.toISOString() === dateB.toISOString();  

isSameDate(new Date(2010, 10, 20), new Date(2010, 10, 20)); // true copy code

75,isString

Used to check if the current value is of string type.

const isString = val => typeof val === 'string';  

isString('10'); // true copy code

76,isSymbol

Used to determine if the value of a parameter is of type Symbol.

const isSymbol = val => typeof val === 'symbol';  

isSymbol(Symbol('x')); // true copy code

77,isUndefined

Used to determine if the type of the parameter is Undefined.

const isUndefined = val => val === undefined;  

isUndefined(undefined); // true copy code

78,isUpperCase

Used to determine if the current string is all uppercase.

const isUpperCase = str => str === str.toUpperCase();  

isUpperCase('ABC'); // true  
isLowerCase('A3@$'); // true  
isLowerCase('aB4'); // false copy code

79,isValidJSON

Used to determine if a given string is a JSON string.

const isValidJSON = str => {  
  try {  
    JSON.parse(str);  
    return true;  
  } catch (e) {  
    return false;  
  }  
};  

isValidJSON('{"name":"Adam","age":20}'); // true  
isValidJSON('{"name":"Adam",age:"20"}'); // false  
isValidJSON(null); // true copy code

80,last

This function returns the last element of the array.

const last = arr => arr[arr.length - 1];  

last([1, 2, 3]); // 3 Copy code

81,matches

This function is used to compare two objects to determine if the first object contains the same attributes and values as the second object.

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 }); // true  
matches({ hair: 'long', beard: true }, { age: 25, hair: 'long', beard: true }); // false copy code

82,maxDate

This code snippet looks for the largest date in the date array to output.

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 Copy Code

83,maxN

The maximum number of first n bits in the output array of this code.

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] Copy Code

84,minDate

This code snippet looks for the earliest date in the date array to output.

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

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