MultiValueDictKeyError at /backendurl/

Hi,

I am trying to get the time spent on each page in a django project using Javascript. I keep getting an error so I am trying to fix it

the error:

MultiValueDictKeyError at /backendurl/
'timeSpent'

Highlighted line of error in views.py:

    timeSpent = request.POST['timeSpent'] 

Here is the javascript in template:

<script>
$(document).ready(function() {
  var startDate = new Date();

  $(window).unload(function() {
      var endDate = new Date();
      $.ajax({
        type: POST,
        url: "backendurl", // be mindful of url names
        data: {
          'timeSpent': endDate - startDate || 'none' // defaults to a string
        },
        success: function(response) {

          // unpack response:
          status = response.status

        }
      })
</script>

Here is the views.py:

def my_view_function(request):
    timeSpent = request.POST['timeSpent']
    response = json.dumps({
        'timeSpent' : timeSpent,
    })
    return HttpResponse(response)

Here is the url.py

    path('backendurl/', views.my_view_function, name='backendurl'),