Advanced Web Design: A Primer

Client-side Technologies

Let’s now take a look at the currently available client-side technologies. Remember, the one thing all of these technologies have in common is that they require the browser to do something other than read pure HTML to display a Web page.

JavaScript (also: JScript, ECMAScript)

This is a programming language that Web browsers understand. Originally developed by Netscape under the name LiveScript, JavaScript is a relatively simple programming language that may be embedded in Web pages. Like most simple programming languages designed to run inside another program, JavaScript is known as a “scripting language”.

An HTML Web page can also contain JavaScript code, which the Web browser runs once the Web page has been received from the Web server. JavaScript lets a Web page author do things like make page elements responsive to user actions (e.g. changing an image when the user moves the mouse cursor over it) and conditions on the user's computer (e.g. displaying "good evening!" on the Web page if the computer's system clock says it's after 6PM and before midnight).

JavaScript can do a lot of fun things, but for security and privacy reasons is limited in many ways. Cross-browser compatibility is also an issue, as the JavaScript support in some browsers is not the same as the JavaScript support in others. For this reason, some features of JavaScript that only work on Internet Explorer or Netscape (but not both) are rarely used.

Microsoft actually calls their version of JavaScript “JScript”, to explain these slight differences between the language in Netscape and Internet Explorer. Both of these browsers (and others, such as Opera), are gradually moving to make their implementations compatible with the ECMAScript standard – a browser-independent definition of what should work how in these languages.

JavaScript is often confused with Java, when they are actually two different programming languages, suited to different purposes. The reason for their similar names is generally attributed to the fact that they are both used in Advanced Web design; however, the languages themselves actually do look quite similar. If you’ve ever written computer programs in C, C++, or Java, you won’t find JavaScript hard to learn at all. Even if you’re completely new to JavaScript, though, it’s not that difficult to learn.

Resources:

• JavaScript 101 on Sausage Island
• Thaus JavaScript Tutorial on Webmonkey
• JavaScript Primer on Website Abstraction

VBScript

Internet Explorer browsers support another client-side scripting language similar in scope and purpose to JavaScript, called VBScript. Since VBScript can do little that JavaScript cannot, it is usually best to stick with JavaScript unless you have some special reason to use VBScript.

Resources:

• VBScript Overview on Windows Scripting Technologies