What is JavaScript?

JavaScript is a streamlined scripting language for developing applications for both Web servers & clients. Here’s how JavaScript works: on the client side, Netscape Navigator 2.0 interprets JavaScript statements that are embedded directly into an HTML page. That means that a script can be performed right there on the client computer; there is no need to connect back out to a server to perform the script there. By moving the ability to execute scripts from the server down to the client, the process of adding interactivity to a page is speeded up tremendously.

JavaScript is an interpreted language. This means JavaScript code is not compiled like C code, or even Java code, which first must run through a compiler to create interpreted byte code. Instead, you can write JavaScript code in any text editor and place it directly on an HTML page, and the JavaScript interpreter will read and interpret the code on the fly. That makes it a much simpler language than Java for simple scripting. It also enables you to view the source of an HTML page in a Web browser and see the JavaScript code right alongside the HTML tags.

Client side JavaScript programs can do a number of interesting things:

• Locally verify form input, notifying the user with a dialog box if the input is invalid.
• Create small stand-alone applications, such as calculators, color pickers, and more...
• Eventually, though not in its initial form, you will be able to use JavaScript to communicate with Java applets and inline plug-ins.