error: function (xhr) {
      console.log(xhr);
      if (xhr.readyState === 4) {
          if (xhr.status === 404) {
              swal({
                  type: 'error',
                  title: 'Oops...',
                  text: xhr.responseJSON.error,
              });
          } else {
              swal({
                  type: 'error',
                  title: 'Oops...',
                  text: 'Something went wrong!',
              });
          }
      }
  }