function addToCart(e, id, qty_id = null) {
  e.preventDefault();
  // quantity check
  var qty = 1;
  if (qty_id) {
    qty = $(qty_id).val();
  }
  $.ajax({
    url: "/cart/add_to_cart",
    type: "POST",
    beforeSend: function(xhr) {xhr.setRequestHeader('X-CSRF-Token', $('meta[name="csrf-token"]').attr('content'))},
    data: {
      id: id,
      qty: qty
    },
    cache: false
  });
};

function changeQty(id, qty, from) {
  $.ajax({
    url: "/cart/change_qty",
    type: "POST",
    beforeSend: function(xhr) {xhr.setRequestHeader('X-CSRF-Token', $('meta[name="csrf-token"]').attr('content'))},
    data: {
      id: id,
      qty: qty,
      ca: from
    },
    cache: false
  });
}