jQuery returning parsererror for ajax request

Question

Been getting a  parsererror  from jquery for an Ajax request  I have tried changing the POST to a GET  returning the data in a few different ways  creating classes  etc   but I cant seem to figure out what the problem is   My project is in MVC3 and I m using jQuery 1 5 I have a Dropdown and on the onchange event I fire off a call to get some data based on what was selected   Dropdown   this loads the  Views  from the list in the Viewbag and firing the event works fine          var viewHtmls   new Dictionary lt string  object gt         viewHtmls Add  data-bind    value  ViewID        viewHtmls Add  onchange    javascript PageModel LoadViewContentNames         Html DropDownList  view    List lt SelectListItem gt  ViewBag Views  viewHtmls    Javascript   this LoadViewContentNames   function            ajax           url    Admin Ajax GetViewContentNames           type   POST           dataType   json           data    viewID      view   val              success  function  data                alert data                      error  function  data                debugger              alert  Error                           The above code successfully calls the MVC method and returns      ViewContentID  1  Name   TopContent   Note   Content on the top       ViewContentID  2  Name   BottomContent   Note   Content on the bottom      But jquery fires the error event for the   ajax   method saying  parsererror

User · Answer

I was also getting  Request return with error parsererror   in the javascript console  In my case it wasn  t a matter of Json  but I had to pass to the view text area a valid encoding     String encodedString   getEncodedString text  encoding     view setTextAreaContent encodedString

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The problem  window JSON parse raises an error in   parseJSON function    lt pre gt    parseJSON  function  data            Attempt to parse using the native JSON parser first if   window JSON  amp  amp  window JSON parse     return window JSON parse  data           lt  pre gt    My solution  Overloading JQuery using requirejs tool    lt pre gt  define   jquery    jquery overload    function            Loading jquery overload      lt  pre gt    jquery overload js file content   lt pre gt  define   jquery   function               parseJSON  function  data                Attempt to parse using the native JSON parser first              THIS RAISES Parsing ERROR         if   window JSON  amp  amp  window JSON parse                 return window JSON parse  data                                   if   data     null                 return data                     if   typeof data      string                      Make sure leading trailing whitespace is removed  IE can t handle it              data     trim  data                 if   data                        Make sure the incoming data is actual JSON                    Logic borrowed from http   json org json2 js                 if   rvalidchars test  data replace  rvalidescape                             replace  rvalidtokens                             replace  rvalidbraces                                return   new Function   return     data                                                             error   Invalid JSON      data               return          lt  pre gt

User · Answer

I recently encountered this problem and stumbled upon this question   I resolved it with a much easier way   Method One  You can either remove the dataType   json  property from the object literal     Method Two  Or you can do what  Sagiv was saying by returning your data as Json     The reason why this parsererror message occurs is that when you simply return a string or another value  it is not really Json  so the parser fails when parsing it   So if you remove the dataType  json property  it will not try to parse it as Json    With the other method if you make sure to return your data as Json  the parser will know how to handle it properly

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I have encountered such error but after modifying my response before sending it to the client it worked fine     Server side response   JSON stringify    status     code   200   result      JSON stringify result        res send response       Sending to client    Client side success  function res  status        response   JSON parse res      Getting as expected       Do something

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I had the same problem  turned out my web config was not the same with my teammates  So please check your web config   Hope this helps someone

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Make sure that you remove any debug code or anything else that might be outputting unintended information   Somewhat obvious  but easy to forgot in the moment

User · Answer

You have specified the ajax call response dataType as        json    where as the actual ajax response is not a valid JSON and as a result the JSON parser is throwing an error    The best approach that I would recommend is to change the dataType to       text    and within the success callback validate whether a valid JSON is being returned or not  and if JSON validation fails  alert it on the screen so that its obvious for what purpose the ajax call is actually failing  Have a look at this     ajax       url    Admin Ajax GetViewContentNames       type   POST       dataType   text       data   viewID      view   val         success  function  data            try               var output   JSON parse data               alert output             catch  e                alert  Output is not valid JSON      data                    error  function  request  error            alert  AJAX Call Error      error

User · Answer

you should remove the dataType   json   Then see the magic    the reason of doing such thing is that you are converting json object to simple string   so json parser is not able to parse that string due to not being a json object     this LoadViewContentNames   function        ajax       url    Admin Ajax GetViewContentNames       type   POST       data    viewID      view   val          success  function  data            alert data              error  function  data            debugger          alert  Error

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Your JSON data might be wrong  http   jsonformatter curiousconcept com  to validate it

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I don t know if this is still actual but problem was with Encoding  Changing to ANSI resolved the problem for me

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If you get this problem using HTTP GET in IE I solved this issue by setting the cache  false  As I used the same url for both HTML and json requests it hit the cache instead of doing a json call     ajax       url    Test Something        type   GET       dataType   json       cache  false      data    viewID      view   val          success  function  data            alert data              error  function  data            debugger          alert  Error

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If you don t want to remove change dataType  json  you can override jQuery s strict parsing by defining a custom converter     ajax          We re expecting a JSON response        dataType   json              but we need to override jQuery s strict JSON parsing     converters             text json   function result                try                      First try to use native browser parsing                 if  typeof JSON      object   amp  amp  typeof JSON parse      function                         return JSON parse result                     else                          Fallback to jQuery s parser                     return   parseJSON result                                   catch  e                      Whatever you want as your alternative behavior  goes here                    In this example  we send a warning to the console and return                    an empty JS object                 console log  Warning  Could not parse expected JSON response                    return                                               Using this  you can customize the behavior when the response cannot be parsed as JSON  even if you get an empty response body      With this custom converter   done   success will be triggered as long as the request was otherwise successful  1xx or 2xx response code

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See the answer by  david-east for the correct way to handle the issue  This answer is only relevant to a bug with jQuery 1 5 when using the file  protocol   I had a similar problem recently when upgrading to jQuery 1 5  Despite getting a correct response the error handler fired  I resolved it by using the complete event and then checking the status value  e g   complete  function  xhr  status        if  status      error      xhr responseText            handleError              else           var data   xhr responseText

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the problem is that your controller returning string or other object that can t be parsed   the ajax call expected to get Json in return  try to return JsonResult in the controller like that    public JsonResult YourAction                    return Json YourReturnObject            hope it helps

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incase of Get operation from web  net mvc api  make sure you are allow get      return Json data JsonRequestBehavior AllowGet

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There are lots of suggestions to remove  dataType   json    While I grant that this works it s ignoring the underlying issue  If you re confident the return string really is JSON then look for errant whitespace at the start of the response  Consider having a look at it in fiddler  Mine looked like this   Connection  Keep-Alive Content-Type  application json  charset utf-8                                                                type   scan   data    image      output  ou      In my case this was a problem with PHP spewing out unwanted characters  in this case UTF file BOMs   Once I removed these it fixed the problem while also keeping  dataType  json

[javascript] jQuery returning "parsererror" for ajax request

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