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http://www.adaptivepath.com/publications/essays/archives/000385.php.
However, the word is really a bit of a misnomer: AJAX doesn't really rely on
XML at all, but rather on a JavaScript function that happens to be named
XMLHttpRequest.
All About XMLHttpRequest.
XMLHttpRequest was originally invented and implemented by a Microsoft
team who were working on a webmail application, and it's been around for a
while now (since 1999, in fact). The reason it has suddenly come to
prominence now is that Google used it in three projects, Gmail, Google
Suggest and Google Maps, and in each case managed to create a much
better user interface than they would have been able to otherwise.
So what does XMLHttpRequest do? To put it simply, it lets your JavaScript go
back to the server, fetch some new content, and write it back out onto the
page – all without the user having to change pages. This gives a 'smoother'
feel to web applications, as they can do things like submit forms without the
whole browser window needing to go blank and reload the page. Take a look
at maps.google.com now, and notice how you can drag the map around
anywhere you want to go without having to reload the page. This would be
unthinkable without XMLHttpRequest.
One of the biggest reasons XMLHttpRequest has become popular now is that
browsers other than Internet Explorer have started to support it, mainly due
to the fuss over its use in Gmail. The function is, by all accounts, a very
simple one in technical terms: it was just a matter of someone having the
idea.
Getting Started with AJAX.
The first thing to do to get started with AJAX, then, is to create an
XMLHttpRequest object in your JavaScript code. As ever, Internet Explorer
has to be difficult, doing this a different way to every other browser out
there. That means that you should use this JavaScript code:
var ajax;
onload = function () {
if (window.ActiveXObject) {
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