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{% if template contains 'product' %}
<script>
jQuery(function($) {
  $('form[action="/cart/add"]').submit(function() {
    var formIsValid = true;
    var message = "Please fill this out and you will be able to add the item to your cart.";
    $(this).find('[name^="properties"]').filter('.required, [required="required"]').each(function() {
      $(this).removeClass('error');
      if (formIsValid && $(this).val() == '') {
        formIsValid = false;
        message = $(this).attr('data-error') || message;
        $(this).addClass('error');
      }
    });
    if (formIsValid){
      return true;
    }
    else {
      alert(message);
      return false;
    }
  }).find('input, select, textarea').focus(function() {
    $(this).removeClass('error');
  });
});
</script>
{% endif %}

<style>
input.error, select.error, textarea.error {
  border-color: red;
}
</style>