Question

I’m writing some JavaScript/AJAX code.

Is there anyway to ensure that the server receives the XML requests in the order that they are sent?

If not with plain Ajax, do I get this guarantee if I send everything over a single WebSocket?

Thanks!

Answer 1

If it is of utmost importance that they’re received in the proper order, and attaching an iterating id to the form isn’t enough:

msg_number = 1; sendAJAX(msg_number);  msg_number++;

Then I’d suggest building your own queue-system, and send each subsequent file as the callback of the previous one.
Rather than each element having its own AJAX-access, create one centralized spot in your application to handle that.

Your different AJAX-enabled sections don’t even need to know that it is a queue:

AJAX.send({ url : "......", method : "post", success : func(){}, syncronous : true });

On the other side of that, you could have something like:

AJAX.send = function (obj) {
    if (obj.synchronous) {
        addToSyncQueue(obj); checkQueue();
    } else { fireRequest(); }
};

Inside of your sync queue, all you’d need to do is wrap a new function around the old callback:

callback = (function (old_cb) {
    return function (response) {
        checkQueue();
        old_cb(response);
    };
}(obj.success));

obj.success = callback;

AJAX.call(obj);

Inside of checkQueue, you’d just need to see if it was empty, and if it wasn’t, use
nextObj = queue.shift(); (if you’re .push()-ing objects onto the queue — so first-in, first-out, like you wanted).