JavaScript (commonly abbreviated JS) is an interpreted programming language, dialect of the ECMAScript standard. It is defined as object-oriented, prototype-based, imperative, loosely typed, and dynamic.

It is mainly used on the client side, implemented as part of a web browser allowing improvements to the user interface and dynamic web pages and server-side JavaScript (Server-side JavaScript or SSJS). Its use in applications external to the web, for example in PDF documents, desktop applications (mostly widgets) is also significant.

Since 2012, all modern browsers fully support ECMAScript 5.1, a version of JavaScript. Older browsers support at least ECMAScript. The sixth edition was released in July 2015.4

JavaScript was designed with a syntax similar to C, although it adopts names and conventions from the Java programming language. However, Java and JavaScript have different semantics and purposes.

All modern browsers interpret the JavaScript code embedded in web pages. To interact with a web page, the JavaScript language is provided with an implementation of the Document Object Model (DOM).

Traditionally it has been used in HTML web pages to perform operations and only within the framework of the client application, without access to server functions. Currently it is widely used to send and receive information from the server together with the help of other technologies such as AJAX. JavaScript is interpreted in the user agent as the statements are downloaded along with the HTML code.