JavaScript is an implementation of the ECMAScript language standard and is primarily used in the form of client-side JavaScript, implemented as part of a web browser in order to provide enhanced user interfaces and dynamic websites. This enables programmatic access to computational objects within a host environment. It can be characterized as a prototype-based object-oriented[6] scripting language that is dynamic, weakly typed and has first-class functions. It is also considered a functional programming language[1] like Scheme and OCaml because it has closures and supports higher-order functions.[7]

JavaScript's use in applications outside web pages—for example in PDF-documents, site-specific browsers and desktop widgets—is also significant.

JavaScript uses syntax influenced by that of C. JavaScript copies many names and naming conventions from Java, but the two languages are otherwise unrelated and have very different semantics. The key design principles within JavaScript are taken from the Self and Scheme programming languages.[8]