JavaScript

JavaScript (JS) is a programming language and core technology of the Web, alongside HTML and CSS. It was created by Brendan Eich in 1995. As of 2025, the overwhelming majority of websites (98.9%) uses JavaScript for client side webpage behavior.

' (XHR') is an API in the form of a JavaScript object whose methods transmit HTTP requests from a web browser to a web server. The methods allow a browser-based application to send requests to the server after page loading is complete, and receive information back. XMLHttpRequest is a component of Ajax programming. Prior to Ajax, hyperlinks and form submissions were the primary mechanisms for interacting with the server, often replacing the current page with another one.

alt=A Firefox browser with a dialog reading "There are about 2502 words on this page."|thumb|350x350px|Demonstration of a bookmarklet that counts the number of words on the page. The browser shown is Firefox 65.0.2 running on Windows 10. A bookmarklet is a bookmark stored in a web browser that contains JavaScript commands that add new features to the browser. They are stored as the URL of a bookmark in a web browser or as a hyperlink on a web page. Bookmarklets are usually small snippets of JavaScript executed when a user clicks on them. When clicked, bookmarklets can perform a wide variety of

programmer, creator of jQuery

library of JavaScript code that allows for easier development of JavaScript-based applications

scripting platform developed by Google

web browser

set of rules that define a JavaScript program

general approach to the use of JavaScript in web pages

browser add-on to block nonfree nontrivial JavaScript

asm.js is a subset of JavaScript designed to allow computer software written in languages such as C to be run as web applications while maintaining performance characteristics considerably better than standard JavaScript, which is the typical language used for such applications.

extension to the JavaScript syntax used by React

CommonJS is a project to standardize the module ecosystem for JavaScript outside of web browsers (e.g. on web servers or native desktop applications).

configuration file

process of removing all unnecessary characters from source code without changing its functionality

Stylesheet language proposed by Netscape

JSFuck is an esoteric subset of JavaScript, where code is written using only six characters: [, ], (, ), !, and +. The name is derived from Brainfuck, an esoteric programming language that also uses a minimalistic alphabet of only punctuation. Unlike Brainfuck, which requires its own compiler or interpreter, JSFuck is valid JavaScript code, meaning that JSFuck programs can be run in any web browser or engine that interprets JavaScript. JSFuck is able to recreate all JavaScript functionality using such a limited set of characters because JavaScript allows the evaluation of any expression as any

computer worm