What is JavaScript?

JavaScript may be a dynamic computer programming language. 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 and static 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 be considered the "assembly language of the Web",^[6] according to its creator and others.

JavaScript may be 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 an interpreted language, but more recent browsers perform just-in-time compilation. JavaScript has been standardized in the ECMAScript language specification.