Thursday, November 08, 2007

IE, XMLHttpRequest, and caching

I recently noticed an oft cited irritation with using XMLHttpRequest in Internet Explorer. Turns out, the browser intercepts HTTP GET requests made from within JavaScript and gives your Ajax application a cached response instead of fresh data.

I was running some tests on scorpion_server, using the JavaScript client in the example that I've packaged with the server, and I noticed that I could change the data stored in a resource when using IE6, but I couldn't get the value I had just set. This means my client-server pair is pretty much useless in IE6 (probably 7 too). But I thought of a solution. IE is just performing a test for exact match when checking the cache, so if any part of the URL is different, IE will actually perform the query like I want it to. So I added a timestamp URL parameter to all GET requests made by the client if the browser is IE, and I configured the server to ignore all URL parameters on GET requests. I wasn't using them anyway, perhaps someday I will, but I don't foresee a need because all I want is a super simple remote data store. (Who knows, YAGNI might just be my new mantra.)

Note that IE was the only browser (of those I tested) that exhibited this annoying behavior. Mozilla based browsers (Firefox, SeaMonkey, Flock), Opera, and Safari all behaved correctly and don't require the timestamp URL parameter hack.
Post a Comment