Ajax Add to Cart with bta.BookingForm

cart.js

function addToCart(e){
  if (typeof e !== 'undefined') e.preventDefault();
  
  // make sure BTA has loaded
  if ($('#add-to-cart').hasClass('bta-load-enable')) {
    alert('Please wait while we look up class availability');
    return false;
  }
  
  var form = $(this).parents('form'), 
      data = [],
      btaForm = form.data('bta.bookingForm');

  if (!btaForm.isValid()) {
    return false;
  }
  
  data.push(["id", form.find('[name="id"]').val()].join('='));
  data.push(["quantity", form.find('[name="quantity"]').val() || 1].join('='));
  btaForm.pushProperties(data);
  
  $.ajax({ 
    type: 'POST',
    url: '/cart/add.js',
    async: false, 
    cache: false, 
    data: data.join('&'),
    dataType: 'json',
    error: addToCartFail,
    success: addToCartSuccess,
    cache: false 
  });
  
}