AJAX Presentation Outline

What is AJAX?

Asynchronous JavaScript + XML
XMLHttpRequest Object
A geek marketing term
Rich Internet Applications with JavaScript

Examples of AJAX

GMail
Google Maps
Basecamp

Is it new?

Not Really
Hidden Frames
IE5+, Mozilla 1.0+, Safari 1.2+, and Opera 7.6+

Why is it popular?

Google helped popularize, and legitimize it in GMail
Increase Usability of Web Applications
Rich Internet Applications without Flash
Save Bandwidth
Download only data you need
Faster interfaces (sometimes)

Why is it bad?

Breaks back button support
URL's don't change as state changes
Cross Browser Issues can be a pain
JavaScript may tax older machines CPU
Can't access domains other than the calling domain
May be disabled (for security reasons) or not availiable on some browsers

Flash vs AJAX

No plugin for AJAX
Flash development tools cost money
Flash typically has slower page load time
Flash can work on older browsers
ActionScript doesn't havea cross browser issues
Flash can access other domains if there is a crossdomain.xml file

XMLHttpRequest

A JavaScript Class that lets you make asynchronous HTTP requests from JavaScript
Make an HTTP request from a JavaScript event
A call back JavaScript function is invoked at each state of the HTTP request and response

XMLHttpRequest Properties

onreadystatechange - call back function for state changes
readyState - the current state of the HTTP call
responseText - the text result of the request
responseXML - DOM xml object from the request
status - HTTP status code of the response
statusText - HTTP status text