jQuery JSON response always triggers a ParseError

I am trying to preform some basic operations with jQuery and JSON. Presently having difficulty with jQuery accepting JSON response from my play framework application. Below is a simplified version of the code that still produces the error.

$.ajax({
    type: 'POST',
    url: "@{FrontEnd.isUsernameAvailable()}",
    data: "name=thisnameisavailable",
    cache: false,
    success: function(data) {
        console.log("Success... ");
    },
    error: function(jqXHR, textStatus, errorThrown) {
        console.log("Error... " + textStatus + "        " + errorThrown);
    },
    dataType: 'json'
});

The error callback is always triggered. It displays

Error... parsererror jQuery15001997238997904205_1298484897373 was not called

Inspecting the returned JSON through Firebug shows no errors and various JSON lint tools also validate. Changing dataType to "text" makes success be called. But I am trying to use the isUsernameAvailable call as part of jQuery validation plugin so I need it to return valid JSON.

Solution 1:

Maybe I'm misunderstanding, but couldn't you set the dataType to text and JSON.parse() the returned data?

success: function(data) {
    data = JSON.parse(data);
    // process data
},

Edited to add generally agreed upon solution (previously a comment only):

I just took a look at api.jquery.com/jQuery.ajax and it looks like with jQuery 1.5 you can do a type conversion of sorts. "multiple, space-separated values: As of jQuery 1.5, jQuery can convert a dataType from what it received in the Content-Type header to what you require. For example, if you want a text response to be treated as XML, use "text xml" for the dataType." Maybe you can try "text json".

Solution 2:

I got the same error as soon as I upgraded to jQuery 1.5. It turns out that my problem is because I'm also using the jquery validation plugin, which is not compatible with jQuery 1.5. If I remove the jquery validation plugin, $.ajax() with dataType json works fine.

More information about the jquery validation plugin incompatibility here: http://bugs.jquery.com/ticket/8118

Solution 3:

I also got "parsererror jQueryNNNN_NNN was not called" (using jsonp and jQuery 1.7.2) The reason was that one of the values in the returned json structure contained newlines. Hope this helps someone.

Solution 4:

I got parseerror, because url contained a callback=? part. This is a magic string which activates JSONP functionality.

As my server side's REST API changed from JSONP to JSON, the data format returned from it was no longer compatible with jQuery.getJSON(..) with callback=?. In this situation, jQuery.getJSON(..) won't call the success callbacks, but the fail callbacks instead.

I resolved this issue by removing the callback=? part from the url parameter.