What is AJAX ?

What is Ajax?

Ajax is a way of developing Web applications that combines:

* XHTML and CSS standards based presentation
* Interaction with the page through the DOM
* Data interchange with XML and XSLT
* Asynchronous data retrieval with XMLHttpRequest,
* JavaScript to tie it all together

Asynchronous?

This is the key. In standard Web applications, the interaction between the customer and the server is synchronous. This means that one has to happen after the other. If a customer clicks a link, the request is sent to the server, which then sends the results back.

With Ajax, the JavaScript that is loaded when the page loads handles most of the basic tasks such as data validation and manipulation, as well as display rendering the Ajax engine handles without a trip to the server. At the same time that it is making display changes for the customer, it is sending data back and forth to the server. But the data transfer is not dependent upon actions of the customer.

Ajax applications do not require installation of a plug-in, but work directly with a Web browser. Because of the technique's reliance on XMLHttpRequest, early applications worked only with Microsoft's Internet Explorer browser, but most other browsers now support Ajax.