Tell Gus what you think, but remember- you are in his home. Be a good guest.

IIRC Google Maps is using a hidden IFRAME for precisely the last of your reasons---IFRAMEs show up in your history.

Posted by Byron Ellis at February 24th 2005 07:36 PM

Cool- thanks for the tip Byron.

Posted by August Mueller at February 24th 2005 07:41 PM

Gus, you might want to add a var declaration to your req variable. Without the "var" bit, the variable is actually a global. This might not matter much, but it is significant.

So you'd have:

var req=getXMLHttpRequest();

instead of

req=getXMLHttpRequest();

Posted by Jeff Watkins at February 25th 2005 05:09 AM

You are half way there Gus :)

You can do this even better. For a few projects I have worked on, I have done something similar to what you have done, except I use closures instead of anonymous functions, and I pass function pointers around too. This makes it a lot cleaner and less crufty with all that status checking that goes on.

You basically have something like this:

function sendRequest(url, callback, errback) {
var req = getXMLHttpRequest();
req.open("GET", url, true);

function dispatch() {
if (req.readyState == 4) {
if (req.status == 200) {
callback();
} else {
errback();
}
}
}

req.onReadyStateChange = dispatch;
}


This way you can pass in custom callbacks, and share the same request/response code. This is just a very simple example. You can (and I have) define RESTian protocols and messaging systems through this kind of methodology.

Anyway, good post.

Posted by Jonathan LaCour at February 25th 2005 06:51 AM