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JavaScript 2.0 is the next major revision of the JavaScript language. Also known as ECMAScript Edition 4, it is being standardized by the ECMA organization. This paper summarizes the needs that drove the revision in the language and then describes some of the major new features of the language to meet those needs — support for API evolution, classes, packages, object protection, dynamic types, and scoping. JavaScript is a very widely used language, and evolving it presented many unique challenges as well as some opportunities. The emphasis is on the rationale, insights, and constraints that led to the features rather than trying to describe the complete language.

JavaScript is a web scripting language invented by Brendan Eich at Netscape. This language first appeared in 1996 as JavaScript 1.0 in Navigator 2.0. Since then the language has undergone numerous additions and revisions, and the most recent released version is JavaScript 1.5. JavaScript has been enormously successful — it is more than an order of magnitude more widely used than all other web client languages combined. More than 25% of web pages use JavaScript. JavaScript programs are distributed in source form, often embedded inside web page elements, thus making it easy to author them without any tools other than a text editor. This also makes it easier to learn the language by examining existing web pages. Download free JavaScript 2 0 Evolving A Language For Evolving Systems here