I am trying to add some items to the cart, but i am getting this error. What am i doing wrong?

function addToCartClicked(event) {   
  var button = event.target
  var shopItem = button.parentElement.parentElement
  var title = shopItem.getElementsByClassName('shop-item-title')[0].innerText
  var price = shopItem.getElementsByClassName('shop-item-price')[0].innerText
  var imageSrc = shopItem.getElementsByClassName('shop-item-image')[0].src
  addItemToCart(title, price, imageSrc) updateCartTotal()
}