gistfile1.js

  var selectCallback = function(variant, selector) {
    if (variant && variant.available) {
      jQuery('#add-to-cart').removeAttr('disabled').removeClass('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, "{{amount_no_decimals}} &#1088;&#1091;&#1073;.") + " <del>" + Shopify.formatMoney(variant.compare_at_price, "{{amount_no_decimals}} &#1088;&#1091;&#1073;.") + "</del>");
      } else {
        jQuery('#price-preview').html(Shopify.formatMoney(variant.price, "{{amount_no_decimals}} &#1088;&#1091;&#1073;."));
      }
      $('#BIS_trigger').hide(); // added for Back In Stock app
    } else {
      jQuery('#add-to-cart').addClass('disabled').attr('disabled', 'disabled'); // set add-to-cart button to unavailable class and disable button
      var message = variant ? "Распродано" : "Unavailable";
      jQuery('#price-preview').text(message);
      $('#BIS_trigger').show();  // added for Back In Stock app
    }
  };