SyntaxError: Unexpected token < in JSON at position 0" 错误在 AJAX

Question

I'm sending data through ajax request and after processing the data an array is returned, which is encoded to json format.

$response = array(
            'data' => $leaveData,
            'message' => 'Event added successfully',
            'status' => 'success'
        );
echo json_encode($response);
exit;

where $leaveData is an associative array:

   Array
(
    [id] => 131
    [user_id] => 134
    [leave_type_id] => 2
    [issued_date] => 2017-10-17
    [leave_from] => 2017-10-25
    [leave_to] => 2017-10-26
    [leave_description] => test
    [leave_status] => 1
)

Here's my ajax request:

$.ajax({
url:"leave/request",
data:{
  id:eventID,
  user_id:empID,
  leave_type:leaveType,
},
  type:"POST",
  cache:false,
  success: function (data, resp){
    var json = data, 
    obj = JSON && JSON.parse(json) || $.parseJSON(json);
  }
});

Also, I think JSON && JSON.parse(json) || $.parseJSON(json) JSON && JSON.parse(json) || $.parseJSON(json) are used for the same purpose?

I have no idea what is going wrong.

Answer 1

I encountered the same problem just a few while ago and the problem lies within the data I was trying to pull into success callback, I just removed the static variables and such that I was trying to get into the json and kept the its values strictly coming only from the query results. Maybe it's the same for you.

Answer 2

You could use the ajax dataType property to interprate JSON directly after ajax response like :

$.ajax({
    url:"leave/request",
    dataType: "json",
    data:{
        id:eventID,
        user_id:empID,
        leave_type:leaveType,
    },
    type:"POST",
    cache:false,
    success: function (data){
        console.log(data);
    }
});

Answer 3

Add an "error" callback to your ajax function, and then print the content:

  error: function(data) {
      console.log("AJAX ERROR:", data);
  }

This will show you what ajax is trying to parse as json.