JavaScript is a programming language designed to interact with elements of web pages. JavaScript consists of three main parts in all the web browsers:

• The DOM (Document Object Model) interacting with elements and contribute interfaces on web pages.
• The BOM (Browser Object Model) contribute the browser API for interacting with the web browser.
• The core functionality using ECMAScripts. 

The programming language JavaScript allows to add interactivity to a web pages. Generally, JavaScript uses with HTML and CSS to refine your web page’s functionality, like showing and displaying interactive charts and maps, database connectivity, validating forms and many more. After HTML and CSS have been downloaded, i.e. web page is full download, JavaScript executes the code the using JavaScript engine in the web browser.

Finally, JavaScript code dynamically (JavaScript engine is a program that executes JavaScript code) convert your HTML and CSS into your interface. Some modern JavaScript engines are compile JavaScript code to bytecode for improved performance of a web page.

Client-side vs. Server-side JavaScript

JavaScript Language can run on both web browsers and servers. When JavaScript program is used on a web page, it will be executed in web browsers. In this case, JavaScript works as a client-side language. A most popular environment JavaScript server-side is Node.js. Server that allows you to access databases, file systems, dynamic content, executes on the Client-side and server-side JavaScripts.

JavaScript History

In 1995, JavaScript was created by a Netscape developer named Brendan Eich. First, its name was Mocha. And then, its name was changed to LiveScript. Netscape decided to change LiveScript to JavaScript to leverage Java’s fame, which was popular. The decision was made just before Netscape released its web browser product Netscape Navigator 2. As a result, JavaScript entered version 1.0.

Netscape released JavaScript 1.1 in Netscape Navigator 3. In the meantime, Microsoft introduced a web browser product called the Internet Explorer 3 (IE 3), which competed with Netscape. However, IE came with its own JavaScript implementation called JScript. Microsoft used the name JScript to avoid possible license issues with Netscape.

Different two JavaScript versions JavaScript in Netscape Navigator and JScript in Internet Explorer are used. 

In 1997, JavaScript 1.1 was submitted to the European Computer Manufacturers Association (ECMA) as a proposal. Technical Committee #39 (TC39) was assigned to standardize the language to make it a general-purpose, cross-platform, and vendor-neutral scripting language. TC39 came up with ECMA-262, a standard for defining a new scripting language named ECMAScript (often pronounced Ek-ma-script). After that, the International Organization for Standardization and International Electrotechnical Commissions (ISO/IEC) adopted ECMAScript (ISO/IEC-16262).