Как сделать подсчет товара в корзине js?

let storageMock = [
    {id: 1, name: "GeForce GTX 980 Ti", price: 9790, amount: 35, amountInCart: 0},
    {id: 2, name: "GeForce GTX TITAN Black", price: 57000, amount: 54, amountInCart: 0},
    {id: 3, name: "AMD EPYC 7742", price: 133120, amount: 44, amountInCart: 0},
    {id: 4, name: "Intel Xeon W-3175X", price: 175000, amount: 23, amountInCart: 0},
    {id: 5, name: "Оперативная память Goodram 4 ГБ", price: 2456, amount: 111, amountInCart: 0},
    {id: 6, name: "Оперативная память Hyper-x 2 ГБ", price: 1456, amount: 123, amountInCart: 0}];
 
let Cart = [{ex:1}];
var Sum = 0;
var Amount = 0;
document.addEventListener("DOMContentLoaded", function() { 
  fillStorageTable(storageMock);
  changeDesc();
  
});
 
function fillStorageTable(items) {
    let storageTable = document.getElementById('storage');
    items.forEach(e => {
      let itemTR = document.createElement('tr');
      itemTR.innerHTML = `<td>${e.id}</td><td>${e.name}</td><td>${e.price}</td><td>${e.amount}</td>`
      itemTR.setAttribute('itemId', e.id);
      storageTable.append(itemTR);
      itemTR.addEventListener('click', addToCart);
    });
}
 
function addToCart(e) {
    let foundedId = e.target.parentElement.getAttribute("itemId");
    Sum += parseInt(this.childNodes[2].textContent.toString());
    document.getElementById('sum').innerHTML = Sum;
    let foundItem = changeDesc(foundedId);
    if (foundItem.amountInCart == 0) {
      let cartTR = document.createElement("tr");
      cartTR.innerHTML = `<td>${foundItem.name}</td><td>${foundItem.price}</td><td>${foundItem.amount}</td>`
      cartTR.setAttribute('id', foundItem.id);
      document.getElementById('cart').append(cartTR);
    } else {
      let bascketTR = document.getElementById(foundedId);
 
    }
    foundItem.amountInCart++;
 }
 
function changeDesc(id) {
  for (var i in storageMock) {
    if (storageMock[i].id == id) {
       return storageMock[i];
    }
  }
}