jquery ajax 200 OK JSON.ParseError

Question

I have a control which has a textbox which, when its content changes, will tricker this javascript function:

page parameter is document.URL as the control has no attached .asxc page and fieldValue is value of the textbox.

function UpdateFieldsOnListSelection(page, fieldValue) {
    $.ajax({
        type: "POST",
        url: page + "/IsSelectedListPictureLibrary",
        data: { "libraryInfo": fieldValue },
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (data) {
            alert("Success!");
        },
        error: function (jqXHR, textStatus, errorThrown) {
            alert("jqXHR: " + jqXHR.status + "\ntextStatus: " + textStatus + "\nerrorThrown: " + errorThrown);
        }
    });
};

It keeps throwing this error:

jqXHR: 200
textStatus: parsererror
errorThrown: SyntaxError: JSON.parse: unexpected character

The code for IsSelectedListPictureLibrary :

[WebMethod]
public static bool IsSelectedListPictureLibrary(string libraryInfo)
{
    if (string.IsNullOrEmpty(libraryInfo)) return false;

    var common = new Utility();
    var storedLibraryInfo = common.GetStoredLibraryInfo(libraryInfo);

    if (storedLibraryInfo == null) return false;

    var web = SPContext.Current.Site.OpenWeb(storedLibraryInfo.WebId);
    var spList = web.Lists[storedLibraryInfo.LibraryId];

    if (spList.BaseTemplate == SPListTemplateType.PictureLibrary)
    {
        web.Dispose();
        return true;
    }

    web.Dispose();
    return false;
}

I have tried changing json in the ajax to jsonp , but same error occured.
I tried changing the format of data .

Any ideas?

Answer 1

尝试从ajax参数中去掉contentType和dataType ，让它们自动识别

Answer 2

Had the same problem with AJAX's 'post' command.

Sent a JSON post request, got a 200 OK repsponse but textStatus was parseerror and errorThrown was SyntaxError: JSON.parse: unexpected character .

This is my JS code:

$.post(url, JSON.stringify(reportVarsJson), function(response) {}, 'json')
.fail(function(jqXHR, textStatus, errorThrown) {
    alert('Error saving report request variables:\n\n' + jqXHR.responseText);
});

The problem turned out to be that my server view (Django) returned an empty response which was not a JSON response.

I changed my server view to return an empty json response and everything works well!

Answer 3

Not sure about [WebMethod], but it seems that the problem is there, and it is related with the output of that method. It has to be a well formed JSON for the ajax method to work. So what I would do is to check call that in a separate window to see the respons and to use something like http://jsonlint.com/ to make sure it is well formed.