It isn't even all that tricky. They just embed a huge, opaque, encoded
state variable for each control in a hidden <input> field in the form.
When the form is posted, they are able to use the state variables to
recreate the application's state on the server side. It provides a
sensation of interactivity that is very impressive.
In my view, the most impressive demonstration of an interactive ("AJAX")
web site that I've encountered is the Google Suggest beta,
Google. If you haven't seen this,
you should look at it, especially if you have web site development
experience. They have to have fabulous round-trip times to make it feel
so responsive.
ยทยทยท
On Tue, 24 Jan 2006 09:01:45 -0800, Don Dwiggins <ddwiggins@advpubtech.com>
For what it's worth, MS' .Net IDE offers something called "code-behind"
for creating web forms. I think they're exploiting a nice trick that
allows a web page in a browser to communicate with the server, without
reloading the page (IIRC, the trick is to use JS to play with an
embedded IFrame, causing it to send requests of a special form to the
server, then interpreting the response). I did something similar, as a
prototype, a few years ago. This allows to maintain a certain amount of
state on the client side during processing of a form.
--
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.