JavaScript is an object-oriented programming language. It contains basic libraries of objects, such as lists, and a set of language elements, such as operators, control structures. JavaScipt can be used for different purposes by supplementing it with additional objects, for example:

- Client side - extends JavaScript by giving objects control over the browser and its DOM (Document Object Model)

For example, it allows an application to place elements on an HTML form and responds to user events such as mouse clicks and page navigation.

- Server side - It extends JavaScript by providing objects relevant to running JavaScript on the server

For example, it allows the application to communicate with the database, ensures the continuity of information transfer from one call to the next application, or performs file manipulation on the server.