What are good ways to ensure AJAX requests called in a certain order get the response in the same order?

While coding a grid based UI for TV listings (at http://tv.burrp.com/scheduler/view.html) I wished the same :). Unfortunately, in a multi-threaded backend there is no guarantee whatsoever on which incoming HTTP request gets executed first. The last request in queue might come back first with a response. There are two possible ways here - Write a simple JS implementation of Queue to stack all the AJAX requests. Fire only when you have received a response for the penultimate one. This also means that you have to use a an AJAX (say XMLHttpRequest) wrapper. This is not what you asked for but might be something worth pondering over - with each AJAX request, you can generate a unique ID on the frontend, send to the server with the request and have it send it back to you in the response. In your frontend you can keep a map of such ID's versus whatever stateful object you want to store against so that you can map the incoming responses (irrespective or order) to these objects.

The jQuery plugin mentioned by looks good. You could also take a look at the IO Queue in YUI http://developer.yahoo.com/yui/3/io/#queue

Hi! try to see these: http://plugins.jquery.com/project/ajaxqueue http://www.protofunc.com/scripts/jquery/ajaxManager/