Recently I needed to evaluate various grid options for a website and to keep things simple I decided to fake/intercept ajax calls to inject the data I needed. I needed something that would let me pass in a wait time and response (in my case 10000 records for a grid) as ajax data and I quickly came up with something like this:

Here is a jsFiddle of the same: Simple ajax fake for mockups

Unfortunately that didn't work for Kendo UI Grid - their code calls jQuery.ajax.extend, which lets them take a little more control of ajax and completely bypasses the above code.

I briefly considered tapping into xmlhttprequest, but a cursory look said that would be a lot of work. Then it occurred to me that jquery ajax uses deferreds under the hood and that I could just hack those instead.

Here is a jsFiddle of the same: jQuery Ajax Intercept

With a little time both examples could be modified to be more generic, but for what I was doing it wasn't really worth it (though I cleaned them up for you a little). Hope this helps.