script.js

/*
 * Example code only. This code has not been tested on a live site.
 * IMPORTANT: Backup your theme before making any modifications.
 *
 */

var selectCallback = function(variant, selector) {
  if (variant && variant.available == true) {
    jQuery('#add-to-cart').removeAttr('disabled'); // remove unavailable class from add-to-cart button, and re-enable button
    if(variant.price < variant.compare_at_price){
      jQuery('#price-preview').html(Shopify.formatMoney(variant.price, "") + " <del>" + Shopify.formatMoney(variant.compare_at_price, "") + "</del>");
    } else {
      jQuery('#price-preview').html(Shopify.formatMoney(variant.price, ""));
    }
    jQuery('#BIS_trigger').hide(); // added for Back In Stock
  } else { // variant does not exist
    jQuery('#add-to-cart').attr('disabled', 'disabled'); // set add-to-cart button to unavailable class and disable button
    var message = variant ? "Sold Out" : "Unavailable";
    jQuery('#price-preview').text(message);
    jQuery('#BIS_trigger').show(); // added for Back In Stock
  }
};