What is Ajax?

I had promised you another post on my predictions for 2006. Well, after listening to feedback (thanks all that have emailed me) it seems that most of you would like to see a deeper dive into technologies that interest me (with diagrams) but in an easy to digest way. So, this is the first in the range of these posts.

What is Ajax?

Introduction

Ajax or Asynchronous JavaScript And XML is a term that describes the use of a combination of existing web technologies to build rich and interactive web pages.

The Main Advantages

• There is no need to fetch a whole page of HTML only the part that has change.
• Most of the processing is performed on the client
• Most of the popular desktop Internet browsers are able to use web pages build in Ajax without any additional add-ins

A Typical Ajax Story

Ajax is comprised of XHTML, Javascript, XMLHTTPRequest object and XML.

In Figure 1, a client side mouse event is recieved by DOM (Document Object Model) which then in turn is captured by Javascript. Javascript initiates the XMLHTTPRequest. All the server has to do is act on the XML query sent in XMLHTTPRequest and respond with its answer in XML. Once received back at the client DOM than parse the received XML and displays the change.

Figure 1 - A Typical Ajax Story

Dave Oliver @ GeeksWithBlogs.Net (c) 2006

Examples in Action

Basic Examples
Typical applications 
Google Maps

Coding

Ajax with .Net
Ajax with Java

Definitive Articles

Jess James Garrett
CNET News

Design Patterns

AjaxPatterns.org - is the best Wiki I’ve found on Ajax design patterns.