Wednesday, June 29, 2005

AJAX - Asynchronous JavaScript and XML

[This was originally posted at]

Until recently, I assumed that web applications were based on a strict client-server / request-response model. This has several limitations, such as a thin client (your web browser) not being able to do any *real* business logic. For example, say you need to validate against a back-end data source such as ensuring a username-password combo is valid or checking if a city exist within a state. As this is really outside the scope of JavaScript, it would require a hit to the backend, and then re-posting the page.

But what if you could just do a "postback" for the desired field only, leaving the rest of the page unchanged? And what if you could have the server automatically update the client without the client initiating the event?

A technology, Asynchronous JavaScript and XML (AJAX) looks like it can do just that. Quoting from Adaptive Path's Jesse James Garrett:


Ajax isn't a technology. It's really several technologies, each flourishing in its own right, coming together in powerful new ways. Ajax incorporates:

  • standards-based presentation using XHTML and CSS;
  • dynamic display and interaction using the Document Object Model;
  • data interchange and manipulation using XML and XSLT;
  • asynchronous data retrieval using XMLHttpRequest;
  • and JavaScript binding everything together.

[End Quote]

Check out these sites for more detail:

This looks like it has a ton of potential, and I'm looking forward to checking it out and doing a future blog post on a sample.

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