I am struggling to resolve this "parsererror" issue with my ajax request

I am currently working on implementing ajax with django. However, I am encountering an error in the response.

When I send a request to the views using ajax and create a model, I encounter issues during the process of creation. It seems like there may be a problem with the return from the views.

The error message I receive is:

fail 200
(index):150 parsererror
(index):151 SyntaxError: Unexpected token a in JSON at position 0
    at parse (<anonymous>)
    at Ut (jquery-3.3.1.min.js:2)
    at k (jquery-3.3.1.min.js:2)
    at XMLHttpRequest.<anonymous> (jquery-3.3.1.min.js:2)

The javascript code (using jquery) looks like this:

$('form').on('submit', function(e){
            let $submit_input = $(this).find('input')
            let $data = $(this).data('group')
            console.log($data);

            e.preventDefault();

            $.ajax({
                'url': "{% url 'groups:ajax_post_add' %}",
                'type': 'POST',
                'data': {
                    'group': $data,
                     csrfmiddlewaretoken: '{{ csrf_token }}',
                },
                'dataType': 'json',
                beforeSend: function(xhr, settings) {
            $submit_input.attr('disabled', true);
            }
          }).then((...args) => { // done
    const [data, textStatus, jqXHR] = args;

    console.log('done', jqXHR.status);
  })
  .catch((...args) => { // fail
    const [jqXHR, textStatus, errorThrown] = args;

    console.log('fail', jqXHR.status);
    console.log(textStatus);
    console.log(errorThrown);
  })
        });

The python code for the views function (GroupRequestAdd) is as follows:

#views
@require_http_methods(["POST"])
def GroupRequestAdd(request):
    group_id = request.POST.get('group')
    group_id = group.objects.get(id=group_id)
    request_add = belong.objects.create(user=request.user,group=group_id)
    return HttpResponse("ajax is done!")

Answer №1

To put it simply, the issue arises from the fact that you are sending back a text string from your Django view instead of a valid JSON string. As a result, your JavaScript code is unable to parse it as "valid" JSON.

The problematic line in your code is

return HttpResponse("ajax is done!")
. To resolve this, you should modify the response to return JSON data.

return HttpResponse(json.dumps({'status': 'ajax is done!'}))

Alternatively, you can adjust your jQuery script to handle HTML responses. This can be achieved by updating the line: 'dataType': 'json', to 'dataType': 'html',.

Answer №2

The issue with the token you are encountering is originating from your python script.

Unexpected token a in JSON at position 0

This indicates that the token found at position 0 is an a and does not adhere to valid JSON formatting.
Upon reviewing your code, it becomes apparent that this diagnosis is accurate as you are returning a string.

return HttpResponse("ajax is done!") // 'a' is the unexpected token at position 0

The dataType attribute within the $.ajax function informs the AJAX operation about the type of data expected in the server response. In this instance, you are anticipating JSON but receiving a string. Consequently, the parse attempt by the $.ajax method fails.

To address this, modify dataType: 'json' to either dataType: 'html' or dataType: 'text' for correct output interpretation.

Refer to the jQuery documentation for guidance on utilizing the dataType property effectively.

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