Back In Stock form for Shopify Simple theme

back-in-stock.liquid

<div class="BIS_container">
	<p>Be the first to know when this is available to order again.</p>
	<input type="text" name="BIS_email" class="BIS_email" placeholder="email address">
	<input type="button" class="btn BIS_button" value="Email when available">
	<p class="BIS_response"> </p>
</div>


<script>
$(function() {
  $('.BIS_container').on('click', '.BIS_button', function(e) { 
    var $container = $(e.delegateTarget),
        email      = $container.find('.BIS_email').val(),
        variantId  = $container.closest('form').find('[name=id]').val();
      
    BISPopover.create(email, variantId).then(function(data) {
      var message = '';
      if (data.status == 'OK') {       
        message = data.message;
      } else {
        for (var k in data.errors) {
          message += data.errors[k].join();
        }
      }
    
      $container.find('.BIS_response').text(message);
    });
  });
  


});
</script>

product.liquid

/* Change Add to cart at line 57 from: */
<input type="submit" value="Add To Cart" id="add" class="btn add-to-cart" />	

/* to: */

{% if product.available %}
   <input type="submit" value="Add To Cart" id="add" class="btn add-to-cart" />	
{% else %}
  <h2>Sold out</h2>
  {% include 'back-in-stock' %}
{% endif %}