What is AJAX?

AJAX may result in a fundamental shift in the way users interact with Web sites. The interaction between a user and a Web server has remained the same since Tim-Berners Lee's first prototype in 1990.

Traditional Web site interaction

The user, by clicking on a link, submitting a form or typing a URL into the browser's location window, causes a request to be sent to a Web server. The server responds with a complete Web page, which replaces the one that the user is currently on. The user progresses from page to page to page, engaged in a "conversation" with the server.

The introduction of JavaScript in late 1995 allowed some interaction to take place completely within the browser (such as form field validation).

How is AJAX different?

AJAX allows JavaScript to send a request to the server and receive and display the response without causing a new page to be displayed. The response from the server can be in the form of plain text, HTML or XML. JavaScript can be used to display the response by modifying to adding to the current page.

With AJAX, the user may have a complete interactive, informative session with a Web site without ever going to a new page.

Why the sudden interest in AJAX?

The fundamental JavaScript method that forms the basis of AJAX is called XMLHttpRequest. This has been available for several years, but only in the Microsoft Internet Explorer browser. Web programmers are reluctant to exploit technology that is only available in one browser. However, this method is now supported in the Firefox browser.

In addition, AJAX is used heavily in the very popular Google Maps system, demonstrating the feasibility and flexibility of the approach.

What does it take to use AJAX?

AJAX is an advanced Web technique and it requires strong skills in JavaScript, particularly the use of the Document Object Model.