Back in Stock form for Supply theme (Shopify)

back-in-stock.liquid

<div class="BIS_form">
  <label for="BIS_email">Email me when restocked</label>
  <input id="BIS_email" name="email" type="email" data-product-id="{{product.id}}" placeholder="your@email.com" value="{{customer.email}}">
  <button class="btn" id="BIS_button">Notify Me</button>
  <p class="BIS_response"> </p>
</div>

<style>
  .BIS_form {
   	background: #f5f5f5; 
    margin: 20px 0;
    padding: 12px;
  }
  
  .BIS_form label {
   	font-weight: bold; 
  }
  
  .BIS_form .BIS_response {
   	margin-top: 1em; 
  }
</style>

<script> 
jQuery(function($) {
	var $container = $('.BIS_form'),
        $response  = $container.find('.BIS_response');
  
	var showMessage = function(msg) { 
      	$response.text(msg);
    };
  
    var responseToMessage = function(data) {
		var msg = '';
 
		if (data.status == 'OK') {
			msg = data.message; // just show the success message
		} else { // it was an error
			for (var k in data.errors) {  // collect all the error messages into a string
				msg += data.errors[k].join();
			}
		}

		return msg;
    };
  
    var toggleForm = function(variant) {
		variant.available ? $container.hide() : $container.show();
    }

	$container.on('click', '#BIS_button', function() { 
		var variantId = Shopify.urlParam('variant'),
			productId = BISPopover.product.id,
            email	  = $container.find('#BIS_email').val();
      
      showMessage('');
      
      BISPopover.create(email, variantId, productId).then(function(data) { 
        showMessage(responseToMessage(data));
      });
	});
  
  	var originalSelectCallback = window.selectCallback;
	window.selectCallback = function(variant, selector) {
      try {
      	toggleForm(variant); 
      }
      finally {
       	originalSelectCallback.apply(window, arguments); 
      }
  	}
});
</script>