Multiple ajax calls from array and handle callback when completed

Question

I have used promises in jQuery slightly before - but I am having trouble applying it to this scenario. I prefer to use the $.when() and $.done() methods to achieve this.

Answer 1

The arguments to $.when should be the return value of $.ajax, which also doesn't need to be called separately -- that makes no sense. You want something like this:

for (i = 0; i < list.length; i++) {
   requests.push($.ajax(...));
}
$.when.apply(undefined, requests).then(...)

The reason that .apply is needed is because $.when can take multiple arguments, but not an array of arguments. .apply expands essentially to:

$.when(requests[0], requests[1], ...)

This also assumes that the requests can be completed in any order.

http://jsfiddle.net/MBZEu/4/ -- notice that 'done' is logged to the console after all of the success messages.