Tutorials References Exercises Videos Menu
Create Website Get Certified Upgrade

JS Tutorial

JS HOME JS Introduction JS Where To JS Output JS Statements JS Syntax JS Comments JS Variables JS Let JS Const JS Operators JS Arithmetic JS Assignment JS Data Types JS Functions JS Objects JS Events JS Strings JS String Methods JS String Search JS String Templates JS Numbers JS BigInt JS Number Methods JS Number Properties JS Arrays JS Array Methods JS Array Sort JS Array Iteration JS Array Const JS Dates JS Date Formats JS Date Get Methods JS Date Set Methods JS Math JS Random JS Booleans JS Comparisons JS If Else JS Switch JS Loop For JS Loop For In JS Loop For Of JS Loop While JS Break JS Iterables JS Sets JS Maps JS Typeof JS Type Conversion JS Bitwise JS RegExp JS Precedence JS Errors JS Scope JS Hoisting JS Strict Mode JS this Keyword JS Arrow Function JS Classes JS Modules JS JSON JS Debugging JS Style Guide JS Best Practices JS Mistakes JS Performance JS Reserved Words

JS Versions

JS Versions JS 2009 (ES5) JS 2015 (ES6) JS 2016 JS 2017 JS 2018 JS 2019 JS 2020 JS 2021 JS IE / Edge JS History

JS Objects

Object Definitions Object Properties Object Methods Object Display Object Accessors Object Constructors Object Prototypes Object Iterables Object Sets Object Maps Object Reference

JS Functions

Function Definitions Function Parameters Function Invocation Function Call Function Apply Function Bind Function Closures

JS Classes

Class Intro Class Inheritance Class Static

JS Async

JS Callbacks JS Asynchronous JS Promises JS Async/Await

JS HTML DOM

DOM Intro DOM Methods DOM Document DOM Elements DOM HTML DOM Forms DOM CSS DOM Animations DOM Events DOM Event Listener DOM Navigation DOM Nodes DOM Collections DOM Node Lists

JS Browser BOM

JS Window JS Screen JS Location JS History JS Navigator JS Popup Alert JS Timing JS Cookies

JS Web APIs

Web API Intro Web Forms API Web History API Web Storage API Web Worker API Web Fetch API Web Geolocation API

JS AJAX

AJAX Intro AJAX XMLHttp AJAX Request AJAX Response AJAX XML File AJAX PHP AJAX ASP AJAX Database AJAX Applications AJAX Examples

JS JSON

JSON Intro JSON Syntax JSON vs XML JSON Data Types JSON Parse JSON Stringify JSON Objects JSON Arrays JSON Server JSON PHP JSON HTML JSON JSONP

JS vs jQuery

jQuery Selectors jQuery HTML jQuery CSS jQuery DOM

JS Graphics

JS Graphics JS Canvas JS Plotly JS Chart.js JS Google Chart JS D3.js

JS Examples

JS Examples JS HTML DOM JS HTML Input JS HTML Objects JS HTML Events JS Browser JS Editor JS Exercises JS Quiz JS Certificate

JS References

JavaScript Objects HTML DOM Objects


ECMAScript 2020

Original JavaScript version numbers were ES5 (2009) and ES6 (2015).

Since 2016 versions are named by year.

New Features in ES2020

Warning

These features are relatively new. Old browser may need an alternative code (Polifill)

JavaScript BigInt

JavaScript BigInt variables are used to store big integer values that are too big to be represented by a a normal JavaScript Number.

JavaScript integers are only accurate up to about 15 digits.

Integer Example

let x = 999999999999999;
let y = 9999999999999999; // too big
Try it Yourself »

BigInt Example

let x = 9999999999999999;
let y = 9999999999999999n;
Try it Yourself »

To create a BigInt, append n to the end of an integer or call BigInt():

Example

let x = 1234567890123456789012345n;
let y = BigInt(1234567890123456789012345)
Try it Yourself »

The JavaScript typeof a BigInt is "bigint":

Example

let x = BigInt(999999999999999);
let type = typeof x;
Try it Yourself »

BigInt is supported in all browsers since September 2020:

Chrome 67 Edge 79 Firefox 68 Safari 14 Opera 54
May 2018 Jan 2020 Jul 2019 Sep 2020 Jun 2018

JavaScript String matchAll()

Before ES2020 there was no string method that could be used to search for all occurrences of a string in a string.

Example

const iterator = text.matchAll("Cats");
Try it Yourself »

If the parameter is a regular expression, the global flag (g) must be set set, otherwise a TypeError is thrown.

Example

const iterator = text.matchAll(/Cats/g);
Try it Yourself »

If you want to search case insensitive, the insensitive flag (i) must be set:

Example

const iterator = text.matchAll(/Cats/gi);
Try it Yourself »

Note

ES2021 introduced the string method replaceAll().



The Nullish Coalescing Operator (??)

The ?? operator returns the first argument if it is not nullish (null or undefined).

Otherwise it returns the second.

Example

let name = null;
let text = "missing";
let result = name ?? text;
Try it Yourself »

The nullish operator is supported in all browsers since March 2020:

Chrome 80 Edge 80 Firefox 72 Safari 13.1 Opera 67
Feb 2020 Feb 2020 Jan 2020 Mar 2020 Mar 2020

The Optional Chaining Operator (?.)

The Optional Chaining Operator returns undefined if an object is undefined or null (instead of throwing an error).

Example

const car = {type:"Fiat", model:"500", color:"white"};
let name = car?.name;
Try it Yourself »

The ?.= operator is supported in all browsers since March 2020:

Chrome 80 Edge 80 Firefox 74 Safari 13.1 Opera 67
Feb 2020 Feb 2020 Mar 2020 Mar 2020 Mar 2020

The &&= Operator

The Logical AND Assignment Operator is used between two values.

If the first value is true, the second value is assigned.

Logical AND Assignment Example

let x = 10;
x &&= 5;
Try it Yourself »

The &&= operator is supported in all browsers since September 2020:

Chrome 85 Edge 85 Firefox 79 Safari 14 Opera 71
Aug 2020 Aug 2020 Mar 2020 Sep 2020 Sep 2020

The ||= Operator

The Logical OR Assignment Operator is used between two values.

If the first value is false, the second value is assigned.

Logical OR Assignment Example

let x = 10;
x ||= 5;
Try it Yourself »

The ||= operator is supported in all browsers since September 2020:

Chrome 85 Edge 85 Firefox 79 Safari 14 Opera 71
Aug 2020 Aug 2020 Mar 2020 Sep 2020 Sep 2020

The ??= Operator

The Nullish Coalescing Assignment Operator is used between two values.

If the first value is undefined or null, the second value is assigned.

Nullish Coalescing Assignment Example

let x = 10;
x ??= 5;
Try it Yourself »

The ??= operator is supported in all browsers since September 2020:

Chrome 85 Edge 85 Firefox 79 Safari 14 Opera 71
Aug 2020 Aug 2020 Mar 2020 Sep 2020 Sep 2020