The W3C DOM offered
the hope of interactivity with the full HTML (and XML) documents with the capability to add
and remove elements via JavaScript. The DOM Level 1 recommendation is fairly well supported
across Mozilla and IE 5+.
The W3C has subsequently come out with versions 2 and 3 of the DOM recommendations,
which continue to build on the functionality defined in level 1. (Differences between the
DOM versions are covered in Chapter 2.)
The Rise of Ajax
The term Ajax, which originally stood for Asynchronous JavaScript and XML, was coined by
Jesse James Garrett of Adaptive Path (www.adaptivepath.com/publications/essays/
archives/000385.php). It was meant to encapsulate the use of a set of technologies under an
umbrella term. At the heart of it is the use of the XMLHttpRequest object, along with DOM
scripting, CSS, and XML.
XMLHttpRequest is a proprietary technology that Microsoft developed in 1998 for its Outlook
Web Access. It is an ActiveX object that enables JavaScript to communicate with the
server without a page refresh. However, it wasn??™t until the rise of Mozilla Firefox and its inclusion
of a native version of XMLHttpRequest that it was used on a large scale. With applications
such as Google Mail starting to take off, other browser developers quickly moved to include it.
Now IE, Firefox, Opera, and Safari all support a native XMLHttpRequest object. With that kind of
ubiquity, it was only inevitable to see the technology take off.
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