Ajax request returns 200 OK but an error event is fired instead of success

Question

I have implemented an Ajax request on my website  and I am calling the endpoint from a webpage  It always returns 200 OK  but jQuery executes the error event  I tried a lot of things  but I could not figure out the problem  I am adding my code below   jQuery Code  var row    1   var json      TwitterId       row           ajax       type   POST       url   Jqueryoperation aspx Operation DeleteRow       contentType   application json  charset utf-8       data  json      dataType   json       cache  false      success  AjaxSucceeded      error  AjaxFailed     function AjaxSucceeded result        alert  hello        alert result d     function AjaxFailed result        alert  hello1        alert result status         result statusText       C  code for JqueryOpeartion aspx  protected void Page Load object sender  EventArgs e        test      private void test         Response Write   lt script language  javascript  gt alert  Record Deleted    lt  script gt         I need the   Record deleted   string after successful deletion  I am able to delete the content  but I am not getting this message  Is this correct or am I doing anything wrong  What is the correct way to solve this issue

User · Answer

If you always return JSON from the server (no empty responses), dataType: 'json' should work and contentType is not needed. However make sure the JSON output...

is valid (JSONLint)
is serialized (JSONMinify)

jQuery AJAX will throw a 'parseerror' on valid but unserialized JSON!

User · Answer

I have the similar problem but when I tried to remove the datatype  json  I still have the problem   My error is executing instead of the Success  function cmd        var data   JSON stringify display1           ajax           type   POST           url    cmd           contentType  application json  charset utf-8             dataType  json           data  data          success  function res                     console log  Success in running run id ajax                         ajax                           type   GET                           url    runid                           contentType  application json  charset utf-8                           dataType  json                           data  data                         success function display runid                                                 error  function req  err   console log  my message      err

User · Answer

This is just for the record since I bumped into this post when looking for a solution to my problem which was similar to the OP s   In my case my jQuery Ajax request was prevented from succeeding due to same-origin policy in Chrome  All was resolved when I modified my server  Node js  to do   response writeHead 200                           Content-Type    application json                Access-Control-Allow-Origin    http   localhost 8080                It literally cost me an hour of banging my head against the wall  I am feeling stupid

User · Answer

I have faced this issue with an updated jQuery library  If the service method is not returning anything it means that the return type is void   Then in your Ajax call please mention dataType  text    It will resolve the problem

User · Answer

I had the same problem  It was because my JSON response contains some special characters and the server file was not encoded with UTF-8  so the Ajax call considered that this was not a valid JSON response

User · Answer

jQuery ajax attempts to convert the response body depending on the specified dataType parameter or the Content-Type header sent by the server  If the conversion fails  e g  if the JSON XML is invalid   the error callback is fired     Your AJAX code contains   dataType   json    In this case jQuery      Evaluates the response as JSON and returns a JavaScript object          The JSON data is parsed in a strict manner  any malformed JSON is   rejected and a parse error is thrown        an empty response is also   rejected  the server should return a response of null or    instead    Your server-side code returns HTML snippet with 200 OK status  jQuery was expecting valid JSON and therefore fires the error callback complaining about parseerror   The solution is to remove the dataType parameter from your jQuery code and make the server-side code return   Content-Type  application javascript  alert  Record Deleted      But I would rather suggest returning a JSON response and display the message inside the success callback   Content-Type  application json    message    Record deleted

User · Answer

Your script demands a return in JSON data type   Try this   private string test       JavaScriptSerializer js   new JavaScriptSerializer     return js Serialize  hello world

User · Answer

I had the same issue  My problem was my controller was returning a status code instead of JSON  Make sure that your controller returns something like   public JsonResult ActionName          Your code    return Json new

User · Answer

You just have to remove dataType   json  from your header if your implemented Web service method is void   In this case  the Ajax call don t expect to have a JSON return datatype

User · Answer

You simply have to remove the dataType   json  in your AJAX call    ajax       type   POST       url   Jqueryoperation aspx Operation DeleteRow       contentType   application json  charset utf-8       data  json      dataType   json          REMOVE THIS LINE            cache  false      success  AjaxSucceeded      error  AjaxFailed

User · Answer

Another thing that messed things up for me was using localhost instead of 127 0 0 1 or vice versa  Apparently  JavaScript can t handle requests from one to the other

User · Answer

I ve had some good luck with using multiple  space-separated dataTypes  jQuery 1 5    As in     ajax       type   POST       url   Jqueryoperation aspx Operation DeleteRow       contentType   application json  charset utf-8       data  json      dataType   text json       cache  false      success  AjaxSucceeded      error  AjaxFailed

User · Answer

Use the following code to ensure the response is in JSON format  PHP version       header  Content-Type  application json    echo json encode  return vars   exit

User · Answer

See this  Its also similar problem  Working i tried    Dont remove dataType   JSON    Note  echo only JSON Formate in PHP file if you use only php echo your ajax code return 200

User · Answer

Try following    ajax       type   POST       url   Jqueryoperation aspx Operation DeleteRow       contentType   application json  charset utf-8       data     Operation     DeleteRow                 TwitterId    1        dataType   json       cache  false      success  AjaxSucceeded      error  AjaxFailed       OR    ajax       type   POST       url   Jqueryoperation aspx Operation DeleteRow amp TwitterId 1       contentType   application json  charset utf-8       dataType   json       cache  false      success  AjaxSucceeded      error  AjaxFailed       Use double quotes instead of single quotes in JSON object  I think this will solve the issue

User · Answer

I reckon your aspx page doesn t return a JSON object  Your page should do something like this  page load   var jSon   new JavaScriptSerializer    var OutPut   jSon Serialize  lt your object gt     Response Write OutPut     Also  try to change your AjaxFailed   function AjaxFailed  XMLHttpRequest  textStatus         textStatus should give you the type of error you re getting

[javascript] Ajax request returns 200 OK, but an error event is fired instead of success

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