JavaScript is an interpreted programming language with object-oriented capabilities. It facilitates web programming and can be embedded in web browsers. Also it allows the object representation of browser window and its contents.

Core JavaScript contains a core set of objects, such as Array, Date, and Math, and a core set of language elements such as operators, control structures, and statements. Client-side JavaScript extends the core language by supplying objects to control a browser and its Document Object Model (DOM). Server-side JavaScript extends the core language by supplying objects relevant to running JavaScript on a server.

JavaScript and Java are entirely different thing. JavaScript can control browser behavior and content. But can not draw graphics or networking or multithreading like Java.

JavaScript Can:

• Control Document appearance and content.
• Control over all behavior of the browser.
• Interact with HTML Forms.
• Interact with the user.
• Read and write client state with cookies.
• Can change the image displayed by IMG tag.
• Interact with objects embedded in the browser.
• Can perform arbitrary computation.
• Allows a block of arbitrary JavaScript code to be executed in a preset interval of time.

Netscape invented JavaScript, and JavaScript was first used in Netscape browsers. However, Netscape is working with ECMA (European Computer Manufacturers Association) to deliver a standardized, international programming language based on core JavaScript. This standardized version of JavaScript, called ECMAScript, behaves the same way in all applications that support the standard. The first version of the ECMA standard is documented in the ECMA-262 specification. The version JavaScript 1.5 is fully compatible with ECMA-262, Edition 3.