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What is JAVACRIPT

As we know that the building blocks for web page is HTML and CSS. HTML (Hyper Text Markup Language) form the skeleton of the web page and CSS is used to decorate it. A web page consisting of only HTML and CSS is merely a static page.

JAVASCRIPT adds functionality to this static page and brings some life in it. JavaScript is a scripting language for Web. JavaScript was developed by Netscape Communications Corporation, the maker of the Netscape web browser. JavaScript was the first web scripting language to be supported by browsers, and it is still by far the most popular.

JavaScript, often abbreviated as JS, is a high-level, interpreted programming language. It is a language which is also characterized as dynamic, weakly typed, prototype-based and multi-paradigm. Alongside HTML and CSS, JavaScript is one of the three core technologies of the World Wide Web

Javascript (JS) is a scripting languages, primarily used on the Web. It is used to enhance HTML pages and is commonly found embedded in HTML code. JavaScript is an interpreted language. Thus, it doesn't need to be compiled. JavaScript renders web pages in an interactive and dynamic fashion. This allowing the pages to react to events, exhibit special effects, accept variable text, validate data, create cookies, detect a user’s browser, etc.

JavaScript is almost as easy to learn as HTML, and it can be included directly in
HTML documents.

Here are a few of the things you can do with JavaScript:
  •  Display messages to the user as part of a web page, in the browser’s status line, or in alert boxes
  • Validate the contents of a form and make calculations (for example, an order form can automatically display a running total as you enter item quantities)
  •  Animate images or create images that change when you move the mouse over them
  • Create ad banners that interact with the user, rather than simply displaying a graphic
  • Detect the browser in use or its features and perform advanced functions only on browsers that support them
  • Detect installed plug-ins and notify the user if a plug-in is required
  • Modify all or part of a web page without requiring the user to reload it
  • Display or interact with data retrieved from a remote server
 You can do all this and more with JavaScript, including creating entire applications.

JavaScript is a full-fledged programming language interpreter embedded inside your web browser. You can do anything in JavaScript that a regular language like Java allows. These include:
  • Declare variables
  • Store and retrieve values
  • Define and invoke functions
  • Define your own classes
  • Load and use external modules
  • Write event handlers that respond to user and other events
  • And much more
The web browser loads a web page, parses the HTML and creates what is known as a Document Object Model (DOM) from the contents. The DOM presents a live view of the web page to your JavaScript code. Your code can then make updates to the DOM and have it presented instantly to the user. The browser also allows you to register your code to be notified on user interface events such as mouse movement, button click, etc. Using all these facilities, you can build cool little (and not so little) applications to serve whatever purpose you may choose.

 Since JavaScript is such a powerful language, it is also possible to write malware, viruses, browser hijackers and other nastiest to inflict them on the users. These range from stealing browser cookies, passwords, credit cards to downloading viruses onto your computer.

Mostely JavaScript is used to write client side code for the web pages but due to enormous development in this language server side scripting also can also be done. Most popular environment for creating server side programs in JavaScript is Node.js