Question

console.log(data) gives the following results

{
    "ERRORS": [
        {
            "MESSAGE": "Error on API.",
            "CODE": "hermes05"
        }
    ],
    "DATA": {}
}

When I try to get the value message out I get undefined, why?

error: function(data){

  console.log(data.ERRORS[0].MESSAGE);

}

FULL CODE

 $.ajax({
                type: "POST",
                dataType: "json",
                url: "http://api.domain.com/something",
                data: {
                    // Send value in mobile input field.
                    mobile:  $("#mobileNo").val()
                },

                success: function(data){

                },

        error: function(data){

             console.log(data.ERRORS.MESSAGE);

                }
            });


            // stop button from submitting.
            event.preventDefault(); // cancel default behavior
        });

Answer 1

What you want is

error: function(jqXhr) {
  try {
    data = JSON.parse(jqXhr.responseText);
    console.log(data.ERRORS[0].MESSAGE);
  } catch (err) {
    console.log("Response was not valid JSON");
  }
}

Check out the difference between success and error at http://api.jquery.com/jQuery.ajax/