WMLScript Introduction

What is WMLScript?

WMLScript (Wireless Markup Language Script) is the client-side scripting language of WML (Wireless Markup Language). A scripting language is similar to a programming language, but is of lighter weight. With WMLScript, the wireless device can do some of the processing and computation. This reduces the number of requests and responses to/from the server. In the old days, fewer round-trips can improve the performance of your WAP site significantly since data transmission over wireless networks is slow. Today, the performance gained may not be so significant any more as data transmission speed has improved a lot. However, you may still find WMLScript useful since putting some operations at the client-side can reduce the load of your servers.

WMLScript is based on ECMAScript (European Computer Manufacturers Association Script), which is JavaScript's standardized version. So, the syntax of WMLScript is very similar to JavaScript. (In case you do not know, JavaScript is a scripting language commonly used on the web.) If you have some programming experience with JavaScript, you should be able to learn WMLScript quickly. You may glance through or even skip some parts of this WMLScript tutorial.

A major difference between JavaScript and WMLScript is that JavaScript code can be embedded in the HTML markup, whereas WMLScript code is always placed in a file separated from the WML markup. URLs are used to refer to the actual WMLScript code in the WML document.

WMLScript has a number of standard libraries. They contain a lot of useful functions that you should get familiar with. We will talk about them in later parts of this WMLScript tutorial.

One common use of WMLScript is to validate form data. Another common use is to display message boxes to give alerts and error messages or to ask for confirmation of actions (no round-trip is needed for showing message boxes, which helps save bandwidth and improve the WAP application's response time).

WMLScript MIME Type and File Extension

WMLScript files have the extension ".wmls". The MIME type is "text/vnd.wap.wmlscript".