Is this so hard????

original_code.js

function initializeResizeEvents() {
    jQuery('#select_size').on("change", function(event) {
        var data = jQuery("#select_size option:selected").attr('resize-data');
        window.productPrice.resize = '';
        if (typeof(data) != 'undefined') {
            if (data == 'custom') {} else {
                data = eval('(' + data + ')');
                window.productHeight = data.height;
                window.productWidth = data.width;
            }
            var p_price = Math.ceil((window.productPrice.permeter * (window.productWidth * window.productHeight) / 10000));
            var total_price = Math.ceil(p_price + window.fixed_price);
            window.productPrice.resize = Math.ceil(total_price);
            if (total_price > 0) {
                jQuery('#product-price-869 .price').text(window.productCurrency + Math.round(total_price * 100) / 100);
            } else {
                jQuery('#product-price-869 .price').text(window.productCurrency + Math.round(window.productPrice.main * 100) / 100);
            }
            calculateFinishPrice();
            var weight = Math.round((window.productHeight * window.productWidth / 10000) * 18);
            var marble_count = (window.productHeight * window.productWidth / 10000) * 11;
            var pounds = Math.ceil(2.20462 * weight);
            var shippingPrice = Math.ceil(weight * window.shippingCost)
            jQuery("#shipping-calculated-price").html(window.productCurrency + shippingPrice);
            jQuery("#attr-tile_count").html(Math.ceil(marble_count * 1000));
            var thickness = jQuery("#attr-thickness").html().replace(/^\D+/g, '');
            if (window.cminch == 'in') {
                jQuery("#attr-weight").html(pounds + " Pounds " + "(" + weight + " kg )");
                jQuery("#attr-dimension").html(Math.round(window.productWidth * 0.393701) + " W x " + Math.round(window.productHeight * 0.393701) + ' H inch');
                jQuery("#attr-thickness").html(window.thickness + ' inch');
            } else {
                jQuery("#attr-weight").html(weight + " kg " + "(" + pounds + " Pounds)");
                jQuery("#attr-dimension").html(window.productWidth + ' W x ' + window.productHeight + ' H cm');
                jQuery("#attr-thickness").html((window.thickness * 2.54) + " cm");
            }
        }
    });
}

refactor.js

function initializeResizeEvents() {
  var $ = jQuery;
  var select = jQuery('#select_size');
  select.on("change", (event) =>
  {
    var data = select.find("option:selected").attr('resize-data');
    window.productPrice.resize = '';
    if (data !== undefined)
    {
      if (data !== 'custom')
      {
        data = eval('(' + data + ')');
        window.productHeight = data.height;
        window.productWidth = data.width;
      }

      var square = window.productWidth * window.productHeight / 10000;
      var p_price = window.productPrice.permeter * square;
      
      var total_price
        = window.productPrice.resize
        = Math.ceil(p_price + window.fixed_price);

      var displayed_price
        = total_price > 0
        ? total_price.toFixed(2)
        : window.productPrice.main.toFixed(2);

      $('#product-price-869 .price')
        .text
        (
          window.productCurrency
          +
          displayed_price
        )

      calculateFinishPrice();

      var weight = Math.round(square * 18);
      var marble_count = square * 11;
      var pounds = Math.ceil(2.20462 * weight);
      var shippingPrice = Math.ceil(weight * window.shippingCost)

      $("#shipping-calculated-price").html(window.productCurrency + shippingPrice);
      $("#attr-tile_count").html(Math.ceil(marble_count * 1000));

      var thickness = $("#attr-thickness").html().replace(/^\D+/g, '');

      var lang =
      [
        [
          "Pounds",
          "kg",
        ],
        [
          'inch',
          'cm',
        ],
        [
          0.393701,
          1,
        ],
        [
          1,
          2.54,
        ]
      ];

      var index = window.cminch == 'in' ? 0 : 1;

      index
        ? jQuery("#attr-weight").html(pounds + " Pounds " + "(" + weight + " kg )")
        : jQuery("#attr-weight").html(weight + " kg " + "(" + pounds + " Pounds)");

      $("#attr-dimension").html(Math.round(window.productWidth * lang[2][index]) + " W x " + Math.round(window.productHeight * lang[2][index]) + ' H ' + lang[1][index]);
      $("#attr-thickness").html((window.thickness * lang[3][index]) + ' ' + lang[1][index]);
    });
}