run ajax requests by order

With these it helps First, keep in mind that the server itself might not return responses in the order the requests are received. Imagine if you fire a complicated ajax request first, and a simple on second (perhaps referencing some cached static data). The second request will probably return before the complicated one returns. You can see how this complicates things; if the order the requests are received is not the same as the order the responses come back, how can one make assurances?
You have some options:

Hope that helps 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++;

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

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

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

obj.success = callback;

AJAX.call(obj);

wish help you to fix your issue The problem is in handleSuccess -- it augments jsonResultArray for every result, and invokes the callback each time:

jsonResultArray.push(jsonResult)
this.fCallback(jsonResultArray);

it should still fix some issue If you create a promise up front, you could keep chaining off of it to get your desired effect.

// ajax mock
function sendRequest(v, delay) {
    var def = $.Deferred();
    setTimeout(function () {
        def.resolve(v);
    }, delay);
    return def.promise();
}

var ajaxPromise = $.Deferred().resolve().promise();
var delay = 600; // will decrement this with each use to simulate later requests finishing sooner

// think of this as a click event handler
function doAction (btnName) {
    delay -= 100;
    var promise = sendRequest(btnName, delay);
    ajaxPromise = ajaxPromise.then(function () {
        return promise;
    }).done(function () {
        console.log(btnName);
    });
}

doAction("1");
doAction("2");
doAction("3");

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

var ajaxPromise = $.Deferred().resolve().promise();
$('#button1').click(function(){
  var promise = $.ajax({url: 'dosomething1.html'})

  ajaxPromise = ajaxPromise.then(function () {
    return promise;
  }, function () {
    return promise; // to also handle fail conditions gracefully
  }).done( function(){ console.log('something 1 success'); } )
    .fail( function(){ console.log('something 1 failure'); } );
});

// repeat for other two buttons

I think the issue was by ths following , AJAX requests are asynchronous, so you cannot guarantee an order if you trigger them as siblings like this.
In order to guarantee a fixed order, you need to make the subsequent call from the success block of its predecessor. Something like this:

$.post('/ajax/method1', { params: params }, 
  function(result) {
    $.post('/ajax/method2', { params: params }, 
      function(result) {
        $.post('/ajax/method3', { params: params }, 
          function(result) {
          });
      });
  });