Java Script Language

Overview

This document is an introduction to the JavaScript Programming Language for professional programmers. It is a small language, so if you are familiar with other languages, then this won't be too demanding.

JavaScript is not Java. They are two very different languages. JavaScript is not a subset of Java. It is not interpreted Java. (Java is interpreted Java!) JavaScript shares C-family syntax with Java, but at a deeper level it shows greater similarity to the languages Scheme and Self. It is a small language, but it is also a suprisingly powerful and expressive language.You should take a look at it. You will find that it is not a toy language, but a full programming language with many distinctive properties.

JavaScript is a regular language which won't take much time to learn. It is better suited to some tasks, such as client programming, than Java is. In my own practice, I have found that working with JavaScript has made me a better Java programmer because it introduced me to a useful set of dynamic techniques.

When JavaScript was first introduced, I dismissed it as being not worth my attention. Much later, I took another look at it and discovered that hidden in the browser was an excellent programming language. My initial attitudes were based on the initial positioning of JavaScript by Sun and Netscape. They made many misstatements about JavaScript in order to avoid positioning JavaScript as a competitor to Java. Those misstatements continue to echo in the scores of badly written JavaScript books aimed at the dummies and amateurs market.

History

JavaScript was developed by Brendan Eich at Netscape as the in-page scripting language for Navigator 2. It is a remarkably expressive dynamic programming language. Because of its linkage to web browsers, it instantly became massively popular. It never got a trial period in which it could be corrected and polished based on actual use. The language is powerful and flawed.

This document describes ECMAScript Edition 3 (aka JavaScript 1.5). Microsoft and Netscape are developing a static revision which does not correct the language's flaws. That new language is not JavaScript and is beyond the scope of this document.

JavaScript is THE scripting language of the Web.

JavaScript is used in millions of Web pages to add functionality, validate forms, detect browsers, and much more.