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Ajax, which consists of HTML, JavaScript? technology, DHTML, and DOM, is an outstanding approach that helps you transform clunky Web interfaces into interactive Ajax applications. The author, an Ajax expert, demonstrates how these technologies work together -- from an overview to a detailed look -- to make extremely efficient Web development an easy reality. He also unveils the central concepts of Ajax, including the XMLHttpRequest object.
Five years ago, if you didn't know XML, you were the ugly duckling whom nobody talked to. Eighteen months ago, Ruby came into the limelight and programmers who didn't know what was going on with Ruby weren't welcome at the water cooler. Today, if you want to get into the latest technology rage, Ajax is where it's at.
However, Ajax is far more than just a fad; it's a powerful approach to building Web sites and it's not nearly as hard to learn as an entire new language.
Before I dig into what Ajax is, though, let's spend just a few moments understanding what Ajax does. When you write an application today, you have two basic choices:
- Desktop applications
- Web applications
These are both familiar; desktop applications usually come on a CD (or sometimes are downloaded from a Web site) and install completely on your computer. They might use the Internet to download updates, but the code that runs these applications resides on your desktop. Web applications -- and there's no surprise here -- run on a Web server somewhere and you access the application with your Web browser.
More important than where the code for these applications runs, though, is how the applications behave and how you interact with them. Desktop applications are usually pretty fast (they're running on your computer; you're not waiting on an Internet connection), have great user interfaces (usually interacting with your operating system), and are incredibly dynamic. You can click, point, type, pull up menus and sub-menus, and cruise around, with almost no waiting around.
On the other hand, Web applications are usually up-to-the-second current and they provide services you could never get on your desktop (think about Amazon.com and eBay). However, with the power of the Web comes waiting -- waiting for a server to respond, waiting for a screen to refresh, waiting for a request to come back and generate a new page.
Obviously this is a bit of an oversimplification, but you get the basic idea. As you might already be suspecting, Ajax attempts to bridge the gap between the functionality and interactivity of a desktop application and the always-updated Web application. You can use dynamic user interfaces and fancier controls like you'd find on a desktop application, but it's available to you on a Web application.
So what are you waiting for? Start looking at Ajax and how to turn your clunky Web interfaces into responsive Ajax applications.
- Old technology, new tricks
- The XMLHttpRequest object
- Adding in some JavaScript
- Finishing off with the DOM
- Putting it together
AJAX is not a new programming language, but a technique for creating better, faster, and more interactive web applications.
With AJAX, your JavaScript can communicate directly with the server, using the JavaScript XMLHttpRequest object. With this object, your JavaScript can trade data with a web server, without reloading the page.
AJAX uses asynchronous data transfer (HTTP requests) between the browser and the web server, allowing web pages to request small bits of information from the server instead of whole pages.
The AJAX technique makes Internet applications smaller, faster and more user-friendly.
- JavaScript
- XML
- HTML
- CSS