Restrict availability when variant option being used for number of attendees

booking-form.liquid

<script>
  $('form[action="/cart/add"]').on('bta.datetimeChange', function(event, form) {
    // restrict number of attendees dropdown to only allow available number of seats
    var qtySelector = $('.single-option-selector:first'),
        max = form.getAvailability(),
        currentQty = parseInt(qtySelector.val(), 10);
    
    qtySelector.find('option').removeAttr('disabled');
    qtySelector.find('option').filter(function () {
      return parseInt(this.value, 10) > max;
    }).prop('disabled', true);
    
    qtySelector.css('border-color', '');
    $('#attendees-updated').remove();
    
    if (currentQty > max) {
      var maxAvailable = qtySelector.find('option').not(':disabled').last().val();
      if (maxAvailable) {
        qtySelector.val(maxAvailable);
        qtySelector.css('border-color', 'red');
        qtySelector.parents('.selector-wrapper').append('<p id="attendees-updated"><small><b>Note:</b> Number of spots updated based on availability</small></p>');
      }
    }
  });    
</script>