Lesson 12. Introducing JavaScript

JavaScript is a scripting language for adding functionality to HTML pages. Its scripts are embedded in HTML files and run completely within the browser. JavaScript turns the browser into an application that runs other applications, rather than one that just displays documents. Support for JavaScript is included in Netscape, Internet Explorer, Mozilla Firefox, and Opera. The ongoing evolution of JavaScript is being managed by ECMA, a European standards body.

As with most technologies in use on the Internet, and especially the World Wide Web, JavaScript is under constant development. It moved rapidly from version 1.0 in Netscape Navigator 2 to version 1.1 in Navigator 3, version 1.2 in Navigator 4, version 1.3 in Navigator 4.5, and version 1.5 in Netscape 6. Meanwhile, Microsoft introduced JScript, its own variation on JavaScript that was first supported in Internet Explorer 3.0. Each of these variations and versions has subtle differences and inconsistencies. Instead of dealing with these differences, this discussion of JavaScript looks at the basic features that are common to all implementations of JavaScript.

In this Lesson

Today, you learn about the basics of JavaScript by exploring the following topics:

• What JavaScript is

• Why you would want to use JavaScript

• The <script> tag

• Basic commands and language structure

• Basic JavaScript programming