Pete Freitag Pete Freitag

AJAX Presentation Outline

Updated on November 17, 2023
By Pete Freitag

Here's an outline of the presentation on AJAX that I gave today at my ColdFusion users group meeting.

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


  • 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

XMLHttpRequest Example

if (window.XMLHttpRequest) {
       var req = new XMLHttpRequest();
       req.onreadystatechange = requestStateHandler;"GET", "/somefile.xml", true);

function requestStateHandler() {
 if (req.readyState == 4) { //response ready

IE does it different

  • The above example however won't work on IE
    • req = new ActiveXOjbect("Microsoft.XMLHTTP");
    • You can't totally blame them because they invented it
    • Native XMLHttpRequest support should be in IE7

Cross Browser AJAX

var req;

function loadXMLDoc(url) {
	req = false;
    // branch for native XMLHttpRequest object
    if(window.XMLHttpRequest) {
    	try {
			req = new XMLHttpRequest();
        } catch(e) {
			req = false;
    // branch for IE/Windows ActiveX version
    } else if(window.ActiveXObject) {
       	try {
        	req = new ActiveXObject("Msxml2.XMLHTTP");
      	} catch(e) {
        	try {
          		req = new ActiveXObject("Microsoft.XMLHTTP");
        	} catch(e) {
          		req = false;
	if(req) {
		req.onreadystatechange = processReqChange;"GET", url, true);

Source: - a great AJAX tutorial BTW.

AJAX Libraries

  • Many people opt for AJAX libraries. This can ease development, but also adds bloat.
    • Prototype is was a popular JS library
    • For ColdFusion there is CFAjax

Prototype Example

I posted the AJAX prototype example that I showed in the presentation in another entry.

ajax presentation xmlhttprequest javascript xml

AJAX Presentation Outline was first published on December 13, 2005.

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