formHijack.js

  // hijack the form submit to add a callback.
  $('#appointment-form').submit((event) => {
    $.ajax({
      url: $('#appointment-form').attr('action'),
      type: 'post',
      data: $('#appointment-form').serialize(),
      success: () => {
        $(document.body).toggleClass('appointments-open');
      },
      error: () => {
        $('.appointment__error').toggleClass('appointment__error-visible');
      }
    });

    event.preventDefault();
  });