« Back to Glossary Index

Javascript (not to be confused with Java) is a computer programming language most commonly used to add dynamic functionality to web pages.

Web pages are written first in HTML, which is considered a mostly “static” descriptive language, meaning that HTML is most often used to describe the layout and other characteristics of how a web page should appear. Javascript (and dynamic HTML) adds the ability to define the behavior of a web page – things that the web page itself can actually do all by itself, without needing to communicate back to the web server (although it can if desired).

Javascript is considered a “scripting” language. While the term is somewhat vague, it generally means that Javascript is a programming language used to augment some other environment, such as the display of HTML-based web pages in your web browser.

Most common browsers come with the ability to run Javascript.

Examples of Javascript include most current web-based email clients, which allow you to browse and edit email without needing to reload the web page for every step of the process.

javascript (Wikipedia)

Paradigmevent-driven, functional, imperative
Designed byBrendan Eich of Netscape initially; others have also contributed to the ECMAScript standard
First appearedDecember 4, 1995; 25 years ago (1995-12-04)
Stable release
ECMAScript 2021 (12th edition) Edit this on Wikidata / June 2021; 2 months ago (June 2021)
Preview release
ECMAScript 2022 Edit this on Wikidata / 22 July 2021; 34 days ago (22 July 2021)
Typing disciplineDynamic, weak, duck
Filename extensions
  • .js
  • .cjs
  • .mjs
Major implementations
V8, JavaScriptCore, SpiderMonkey, Chakra
Influenced by
Java, Scheme, AWK, HyperTalk
TypeScript, CoffeeScript, AssemblyScript, ActionScript, Dart, Objective-J, Opa, Haxe

JavaScript (/ˈɑːvəˌskrɪpt/), often abbreviated as JS, is a programming language that conforms to the ECMAScript specification. JavaScript is high-level, often just-in-time compiled, and multi-paradigm. It has curly-bracket syntax, dynamic typing, prototype-based object-orientation, and first-class functions.

Alongside HTML and CSS, JavaScript is one of the core technologies of the World Wide Web. Over 97% of websites use it client-side for web page behavior, often incorporating third-party libraries. Most web browsers have a dedicated JavaScript engine to execute the code on the user's device.

As a multi-paradigm language, JavaScript supports event-driven, functional, and imperative programming styles. It has application programming interfaces (APIs) for working with text, dates, regular expressions, standard data structures, and the Document Object Model (DOM).

The ECMAScript standard does not include any input/output (I/O), such as networking, storage, or graphics facilities. In practice, the web browser or other runtime system provides JavaScript APIs for I/O.

JavaScript engines were originally used only in web browsers, but they are now core components of other software systems, most notably servers and a variety of applications.

Although there are similarities between JavaScript and Java, including language name, syntax, and respective standard libraries, the two languages are distinct and differ greatly in design.

« Back to Glossary Index