Question

I have a pageTest.html in local folder,this page call a service.ashx?i=…(that return value param passed incremented +1) with follow Ajax code:

. . getIncr: function(parameters, success){        $.ajax({                async: false,                 type: methodType,                url: getTarget,                data: 'n='+parameters,                dataType:'jsonp',                success: success              });     } . . 

The html page call this function for m time (with script..):

  .       var start = function(){   .   .   var val = 0;   .         .   for(i=0; i<m; i++)   {       Foo.getIncr(val, function(returned_n){           val = returned_n;       });    }  }; 

During the page loading, the calls are execute in ‘Asynchronous mode’ but i setting ‘async: false‘ in Ajax. I read about this problem and found the reason, that is Ajax can’t synch call from page.html to service.ashx if there are in different domain. Is there a solution for execute Synch call in page.html to that service.ashx (in different domain)?

Answer 1

Well, the problem is that you cannot make synchronous JSONP requests. The way it is implemented is, as Andy pointed out, through a so-called ‘script tag hack’. There is no way jQuery can stop the execution of the javascript application while waiting for a script tag to be filled.

So you are calling the right method of jQuery to make a JSONP request but because it is JSONP, the asynchronous option is not applied and there is no way around it. You have to handle the request asynchronously.

On a side note, it is not a good idea to use $.ajax in synchronous mode anyway. If the request takes too much time to be completed, the browser will stall and chances are your user will get a popup saying the page is not responding.