History of JavaScript
JavaScript is an object-based scripting programming language based on the concept of prototypes. The language is best known for its use in websites, but is also used to enable scripting access to objects embedded in other applications. It is not related to Java besides having C-like syntax. It has far more in common with the Self programming language.
JavaScript was originally developed by Brendan Eich of Netscape Communications Corporation under the name Mocha, then LiveScript, and finally renamed to JavaScript. The change of name from LiveScript to JavaScript roughly coincided with Netscape adding support for Java technology in its Netscape Navigator web browser. JavaScript was first introduced and deployed in the Netscape browser version 2.0B3 in December of 1995. The choice of name proved to be a source of much confusion.
As of 2005, the latest version of the language is JavaScript 1.6 which corresponds to ECMA-262 Edition 3 like JavaScript 1.5, except of Array extras, and Array and String generics. ECMAScript, in simple terms, is a standardized version of JavaScript. Mozilla versions since 1.8 Beta 1 also have partial support of E4X, which is a language extension dealing with XML, defined in the ECMA-357 standard.
JavaScript is a prototype-based scripting language with a syntax loosely based on C. Like C, it has the concept of reserved keywords, which (being executed from source) means it is almost impossible to extend the language without breakage.
Also like C, the language has no input or output constructs of its own. Where C relies on standard I/O libraries, a JavaScript engine relies on a host environment into which it is embedded. There are many such host environment applications, of which web technologies are the most well known examples. These are examined first.
JavaScript embedded in a web browser connects through interfaces called Document Object Model (DOM) to applications, especially to the server side (web servers) and the client side (web browsers) of web applications. Many web sites use client-side JavaScript technology to create powerful dynamic web applications. It may use unicode and can evaluate regular expressions (introduced in version 1.2 in Netscape Navigator 4 and Internet Explorer 4). JavaScript expressions contained in a string can be evaluated using the eval function.
One major use of web-based JavaScript is to write functions that are embedded in or included from HTML pages and interact with the DOM of the page to perform tasks not possible in static HTML alone, such as opening a new window, checking input values, changing images as the mouse cursor moves over, etc. Unfortunately, the DOM interfaces in various browsers differ and don't always match the W3C DOM standards. Different browsers expose different objects and methods to the script. It is therefore often necessary to write different variants of a JavaScript function for the various browsers, though this situation is improving. Major design methodologies using JavaScript to interact with DOM include DHTML, Ajax, and SPA.
Outside of the Web, JavaScript interpreters are embedded in a number of tools. Adobe Acrobat and Adobe Reader support JavaScript in PDF files. The Mozilla platform, which underlies several common web browsers, uses JavaScript to implement the user interface and transaction logic of its various products. JavaScript interpreters are also embedded in proprietary applications that lack scriptable interfaces. Dashboard Widgets in Apple's Mac OS X v10.4 are implemented using JavaScript. Microsoft's Active Scripting technology supports JavaScript-compatible JScript as an operating system scripting language. JScript .NET is a CLI-compliant language that is similar to JScript, but has further object oriented programming features.
Each of these applications provides its own object model which provides access to the host environment, with the core JavaScript language remaining mostly the same in each application.
Javascript Tutorials and Information
Javascript Variables
Javascript Numbers
Javascript Arrays
Javascript Operators
Javascript Control Structures
Javascript Functions
Javascript Objects and Constructors
Javascript Exception Handling
Javascript Whitespace
Javascript Comments
Reference Material
Authoring Guides
Tutorials
Resources
| 
