JavaScript (/ˈdʒɑːvɑːˌskrɪpt/; JS), also known as ECMAScript (the untrademarked name used for the standard), is adynamic programming language.^[5] It is most commonly used as part of web browsers, whose implementations allow client-side scripts to interact with the user, control the browser, communicate asynchronously, and alter the document content that is displayed.^[5] It is also used in server-side network programming with runtime environments such as Node.js, game development and the creation of desktop and mobile applications. With the rise of the single-page web app and JavaScript-heavy sites, it is increasingly being used as a compile target for source-to-source compilers from both dynamic languages andstatic languages. In particular, Emscripten and highly optimised JIT compilers, in tandem with asm.js that is friendly to AOT compilers like OdinMonkey, have enabled C and C++ programs to be compiled into JavaScript and execute at near-native speeds, making JavaScript to be considered the "assembly language of the web",^[6] according to its creator and others.

JavaScript is classified as a prototype-based scripting language with dynamic typing and first-class functions. This mix of features makes it a multi-paradigm language, supporting object-oriented,^[7] imperative, and functional^[1][8] programming styles.

Despite some naming, syntactic, and standard library similarities, JavaScript and Java are otherwise unrelated and have very different semantics. The syntax of JavaScript is actually derived from C, while the semantics and design are influenced by theSelf and Scheme programming languages.^[9]

JavaScript is also used in environments that aren't web-based, such as PDF documents, site-specific browsers, and desktop widgets. Newer and faster JavaScript virtual machines (VMs) and platforms built upon them have also increased the popularity of JavaScript for server-side web applications. On the client side, JavaScript has been traditionally implemented as aninterpreted language, but more recent browsers perform just-in-time compilation.

JavaScript has been standardized in the ECMAScript language specification.