JavaScript is a cross-platform, object-oriented scripting language used to make webpages interactive. There are also more advanced server side versions of JavaScript such as Node.js, which allow you to add more functionality to a website such as realtime collaboration between multiple computers. Inside a host environment (for example, a web browser),

JavaScript contains a standard library of objects, such as Array, Date, and Math, and a core set of language elements such as operators, control structures, and statements. Core JavaScript can be extended for a variety of purposes by supplementing it with additional objects; for example:

Client-side JavaScript extends the core language by supplying objects to control a browser and its Document Object Model (DOM). For example, client-side extensions allow an application to place elements on an HTML form and respond to user events such as mouse clicks, form input, and page navigation.