why callback parameter is added to query string using jQuery AJAX request

Question

I write in MVC and send jQuery AJAX request.

I don't understand why the 'callback' parameter is added to query string when I send AJAX request using JQUERY as below

http://localhost:39224/Test/TAction/2?callback=jQuery151031896859929189747_1301556762907

This causes error when response is returned I have never encountered such a problem. What it can be?

here the request code Thank you

$.ajax({
         type: 'POST',
         dataType: 'json',
         url: 'Test/TAction/' + id,
         async: false,                   
         success: function (data, textStatus, XMLHttpRequest) {
              var branches = $.parseJSON(data);
         },
         error: function (a, b, c) {
              var d = 1;
         }
});

score 2 · Accepted Answer · answered Mar 31 '11 at 08:04

2

As per the docs for the jsonp setting of .ajax():

Override the callback function name in a jsonp request. This value will be used instead of 'callback' in the 'callback=?' part of the query string in the url. So {jsonp:'onJSONPLoad'} would result in 'onJSONPLoad=?' passed to the server. As of jQuery 1.5, setting the jsonp option to false prevents jQuery from adding the "?callback" string to the URL or attempting to use "=?" for transformation. In this case, you should also explicitly set the jsonpCallback setting. For example, { jsonp: false, jsonpCallback: "callbackName" }

I.e., it seems to me that you need to explicitly set jsonp to false if you're using jQuery 1.5+, although I haven't tried it myself.

answered Mar 31 '11 at 08:04

jensgram

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I used hundreds of times **simple** jQuery AJAX request and NEVER encountered such a problem. why it happens?? – theateist Mar 31 '11 at 08:06
@theateist Not sure. Things have changed in 1.5, but I'm not one to say that this is new to 1.5. Does it have an effect to add the `jsonp` setting? – jensgram Mar 31 '11 at 08:08
1

Is some other code on your page using $.ajaxSetup() and setting jsonp? – Douglas Mar 31 '11 at 08:09
jensgram, I found the mistake. Someone updates the version of jQuery to 1.5 and I didn't know it. I'll read about JSONP to resolve the problem. Thank you – theateist Mar 31 '11 at 08:19
@theateist Glad you found the problem :) – jensgram Mar 31 '11 at 08:24
I apologies, but I still have the problem. I noticed that this happens only if 'dataType: 'json'. If I change it to 'dataType: 'html', no **callback** is added and **success** function is called, but I need json. Why it happens only with 'dataType: 'json' – theateist Mar 31 '11 at 09:20
@theateist Well, I guess that's what they're saying in the docs. Did you try `{ ..., jsonp: false }`? – jensgram Mar 31 '11 at 09:22
{..., jsonp: false, jsonpCallback: "fn" }, but I get error "no fn is called" – theateist Mar 31 '11 at 09:57
@theateist `{..., jsonp: false, jsonpCallback: function() {} }` with dummy function? – jensgram Mar 31 '11 at 10:02

score 0 · Answer 2 · answered Mar 31 '11 at 08:21

0

In jQuery-1.5 "?callback" is added automatically so you need to configure jSONP

answered Mar 31 '11 at 08:21

theateist

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why callback parameter is added to query string using jQuery AJAX request

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