AJAX IN DEPTH

Why use Ajax?

Mainly to build a fast, dynamic website, but also to save resources.
For improving sharing of resources, it is better to use the power of all the client computers rather than just a unique server and network. Ajax allows to perform processing on client computer (in JavaScript) with data taken from the server.
The processing of web page formerly was only server-side, using web services or PHP scripts, before the whole page was sent within the network.
But Ajax can selectively modify a part of a page displayed by the browser, and update it without the need to reload the whole document with all images, menus, etc...
For example, fields of forms, choices of user, may be processed and the result displayed immediately into the same page.

Who’s Using Ajax

Google is making a huge investment in developing the Ajax approach. All of the major products Google has introduced over the last year — Orkut, Gmail, the latest beta version of Google Groups, Google Suggest, and Google Maps — are Ajax applications. (For more on the technical nuts and bolts of these Ajax implementations, check out these excellent analyses of Gmail, Google Suggest, and Google Maps.) Others are following suit: many of the features that people love in Flickr depend on Ajax, and Amazon’s A9.com search engine applies similar techniques.

These projects demonstrate that Ajax is not only technically sound, but also practical for real-world applications. This isn’t another technology that only works in a laboratory. And Ajax applications can be any size, from the very simple, single-function Google Suggest to the very complex and sophisticated Google Maps.

At Adaptive Path, we’ve been doing our own work with Ajax over the last several months, and we’re realizing we’ve only scratched the surface of the rich interaction and responsiveness that Ajax applications can provide. Ajax is an important development for Web applications, and its importance is only going to grow. And because there are so many developers out there who already know how to use these technologies, we expect to see many more organizations following Google’s lead in reaping the competitive advantage Ajax provides.

What is Ajax in depth?

Ajax is a set of technologies, supported by a web browser, including these elements:

·     HTML and CSS for presenting.

·     JavaScript (ECMAScript) for local processing, and DOM (Document Object Model) to access data inside the page or to access elements of XML file read on the server (with the getElementByTagName method for example)...

·     The XMLHttpRequest object is used to read or send data on the server asynchronously.

Optionally...

·     DOMParser may be used

·     PHP or another scripting language may be used on the server.

·     XML and XSLT to process the data if returned in XML form.

·     SOAP may be used to dialog with the server.

The "asynchronous" word, means that the response of the server while be processed when available, without to wait and to freeze the display of the page.