An issue occurred when attempting to retrieve JSON data using an Ajax

After making an ajax call below, I encountered an error that left me puzzled. The variable 'response' in the success function is structured as follows:

{"status": "complete", "username": "test", "error": "0", "message": ""}

Surprisingly, when I attempted to display the 'error' key using alert functions within the success function, the first one worked fine but the next two returned 'undefined'. Even though I am aware of the existence of the error key, JavaScript seems unable to recognize it which ultimately led to a crash.

$.ajax({
    url: '/index.php/api/userLogin',
    data: userInfo,
    datatype: 'json',
    async: 'false',
    type: 'POST',
    success: function(response)
    {
      alert(response); //prints correct response
      alert(response.error); //prints undefined
      alert(response["error"]); //prints undefined
    },
    error: function(xhr, status, error) 
    {
    var err = eval("(" + xhr.responseText + ")");
    //alert("Please Try Again, we had an internal error!");
    alert(err.message);
    }
  });

If anyone can shed some light on what might be causing this issue and offer a solution, it would be greatly appreciated.

Answer №1

This issue is a result of two main factors:

  1. The JSON data is being sent by the server with an incorrect content type
  2. Incorrect capitalization is being used when overriding it

As a consequence, jQuery is interpreting the JSON as plain text rather than an object, which explains why alerting the value displays the raw JSON instead of [Object object].

To resolve this problem, ensure that the server sends the JSON with the correct content type:

Content-Type: application/json

If you are using PHP, you can achieve this with the following code:

header("Content-Type: application/json");

Additionally, either remove datatype: 'json' or change it to dataType: 'json'.

Answer №2

Due to the response not being parsed as a JSON object, you can accomplish this by following these steps:

$.ajax({
    url: '/index.php/api/userLogin',
    data: userInfo,
    datatype: 'json',
    async: 'false',
    type: 'POST',
    success: function(response)
    {
      var data = jQuery.parseJSON(response); // <---- Parse as JSON here
      alert(data.error); 
      // Handle data accordingly

    },
    error: function(xhr, status, error) 
    {
    var err = eval("(" + xhr.responseText + ")");
    //alert("Please Try Again, we had an internal error!");
    alert(err.message);
    }
  });

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