gistfile1.html

<script>
$(function() {

  $('.notify_form [type=submit]').click(function(e) {
    e.preventDefault();

    var variantId = $('select[name=id]').val() || {{ product.variants.first.id }};
    var email = $(this).closest('form').find('[name="contact[email]"]').val();
    
    var showResponse = function(text) { 
      var form = $(e.target).closest('form');
      form.find('.BIS_feeback').remove();
      form.append($('<p class="BIS_feeback">').text(text));
    };

    BISPopover.create(email, variantId)
          .then(function(data) { 
            if (data.status == 'OK') { showResponse(data.message) } 
            else { 
              var msg = [];
              for(var i in data.errors) { 
                msg.push(data.errors[i]);
              }
              showResponse(msg.join("\n"));
            } 
            }); 
  });
});
</script>