jQuery101

$(document).ready(function () {
  $(".price,.quantity").on("input", function () {
    let total = 0;
    let quantity = $(this).closest("tr").find(".quantity").val();
    let price = $(this).closest("tr").find(".price").val();
    if (quantity && price) {
      let total = quantity * price;
      let doThis = $(this).closest("tr").find(".total").val(total);
      subTotalSum();
      discountCalc();
    }
  });

  let subTotalSum = function () {
    let sum = 0;
    $(".total").each(function () {
      let num = $(this).val();
      if (num) {
        sum += parseFloat(num);
      }
    });
    $(".sub-total").val(sum);
  };
  let discountCalc = function () {
    let subTotal = $(".sub-total").val();
    let discountProcentage = $(".discount").val();
    let calc = (discountProcentage / 100).toFixed(2);
    let multiply = subTotal * calc;
    let discountFinal = subTotal - multiply;
    $(".all-total").val(discountFinal);
  };

  $(".btnAdd").click(function () {
    let $tableBody = $(".product-table").find("tbody");
    $trLast = $tableBody.find("tr:last");
    $trNew = $trLast.clone(true);
    $trNew.find("input[type=text]").val("");
    $trNew.find("input[type=number]").val("");
    $trLast.after($trNew);
  });
  $(".discount").keyup(function () {
    $(".total-discount").val($(".discount").val() + "%");
    discountCalc();
  });
});