Cart item not displaying added items

"Uncaught TypeError: item.totalPrice is null
    updateCartItems https://splashonline.co.za/js/add-to-cart.js:139
    updateCartItems https://splashonline.co.za/js/add-to-cart.js:132
    <anonymous> https://splashonline.co.za/js/add-to-cart.js:149
    jQuery 2

$(document).ready(function() {
  $(".add-to-cart-btn").click(function(e) {
    e.preventDefault();

    var productId = $(this).data("id");
    var productName = $(this).data("product-name");
    var productImage = $(this).data("product-image");

    // Get quantity from your quantity input element
    var quantity = parseInt($("#quantity-input-" + 
                   productId).val()); // Make sure the ID is correct
    // Get the product price from the data attribute
    var productPrice = parseFloat($(this).data("product-price"));

    // Store the product details in the session
    var cartItems = JSON.parse(sessionStorage.getItem("cartItems")) || [];
    
    cartItems.push({
      productId: productId,
      quantity: quantity,
      productImage: productImage,
      productName: productName,
      totalPrice :totalPrice
    });

    sessionStorage.setItem("cartItems", JSON.stringify(cartItems));

    $.ajax({
      type: "POST",
      url: "add-to-cart.php",
      data: { productId: productId },
      success: function(response) {
        // Debugging: Alert the response to see if it's successful
        alert(response);

        updateCartBadge(); // Update the cart badge with the new count
        getCartItem(); // Refresh the cart items after adding
      },
      error: function(xhr, status, error) {
        alert("An error occurred while adding the item to the cart.");
        console.log(xhr.responseText);
      }
    });
  });
      // Function to update cart badge.
    function updateCartBadge(userId) {
        $.ajax({
            type: "GET",
            url: "getCartItemCount.php",
            data: { userId: userId},
    success: function (response) {
        console.log('Cart Item Count:', response);
        $("#cart-badge").text(response); // Update the cart badge count
    },
    error: function (xhr, status, error) {
        alert("An error occurred while retrieving the cart item count.");
        console.log(xhr.responseText);
    }
});
}

    // function for updating cart items.
    function updateCartItems(cartData) {
        console.log("Response from the server:", cartData);
        var cartItems = cartData.cartItems;
        var cartContainer = document.getElementById("cart-items");
        cartContainer.innerHTML = "";

        cartItems.forEach(function (item) {
            // Create elements to display the cart items
            var itemContainer = document.createElement("tr");

            //column for product-name cart details
            var itemName = document.createElement("td");
            itemName.textContent = item.product_name;
            itemContainer.appendChild(itemName);

            //column for image cart details
            var itemImage = document.createElement("td");
            var image = document.createElement("img");
            image.src = item.product_image;
            image.alt = item.product_name;
            image.classList.add("img-thumbnail");
            itemImage.appendChild(image);
            itemContainer.appendChild(itemImage);

            //column for price cart details
            var itemPrice = document.createElement("td");
            itemPrice.textContent = "$" + item.totalPrice;
            itemContainer.appendChild(itemPrice);

            //column for quantity for cart details.
            var itemQuantity = document.createElement("td");
            itemQuantity.textContent = item.product_qty;
            itemContainer.appendChild(itemQuantity);

            //column for action to remove items.
            var itemAction = document.createElement("td");
            var removeButton = document.createElement("button");
            removeButton.textContent = "Remove";
            removeButton.classList.add("btn", "btn-danger", "btn-sm");
            removeButton.dataset.productId = item.product_id;
            removeButton.addEventListener("click", function () {
                var productId = this.dataset.productId;
                removeItemFromCart(productId);
            });
            itemAction.appendChild(removeButton);
            itemContainer.appendChild(itemAction);

            cartContainer.appendChild(itemContainer);
        });

        var totalPriceContainer = document.getElementById("total-price");
        totalPriceContainer.textContent = "Total Price: R" + cartData.totalPrice;
    }

    // Call the backend to fetch cart data when the cart modal is opened
    $("#cartModal").on("show.bs.modal", function () {
        $.ajax({
            type: "GET",
            url: "getCartData.php",
            dataType: "json",
            success: function (cartData) {
                console.log("Response from the server:", cartData);
                updateCartItems(cartData);
                updateCartBadge();
            },
            error: function (xhr, status, error) {
                alert("An error occurred while fetching cart item details");
                console.log(xhr, responseText);
            }
        });
    });
    
    // function to populate the cart modal with cart items.
    function getCartItemsForModal() {
        $.ajax({
            type: "GET",
            url: "getCartItem.php",
            dataType: "html",
            success: function (response) {
                $("#cart-items").html(response);
            },
            error: function (xhr, status, error) {
                console.log("An error occured while retrieving cart items");
                console.log(xhr.responseText);
            },
        });
    }
    updateCartItems();
    //call getCartItemsForModal function.
    $("#cart-badge-btn").click(function () {
        getCartItemsForModal();
    });

    //function to remove an item from the cart.
    function removeItemFromCart(productId) {
        $.ajax({
            type: "POST",
            url: "removeCartItem.php",
            data: { productId: productId },
            dataType: "json",
            success: function (response) {
                if (response.success) {
                    getCartItemsForModal();
                    updateCartItems();
                } else {
                    alert("An error occured while removing the item from the cart");
                }
            },
            error: function (xhr, status, error) {
                alert("An error occured while removing the item from the cart.");
                console.log(xhr.responseText);
            },
        });
    }

  function getCartItem() {
    $.ajax({
      type: "GET",
      url: "getCartItem.php",
      success: function(response) {
        $("#cart-items").html(response); // Update the cart items on the page
      },
      error: function(xhr, status, error) {
        alert("An error occurred while retrieving the cart items.");
        console.log(xhr.responseText);
      }
    });
  }

  // Call updateCartBadge and getCartItem on page load
  updateCartBadge();
  getCartItem();
});  
});  

<div class="row px-xl-5 pb-3">
            <div class="col-lg-3 col-md-6 col-sm-12 pb-1">
                <div class="card product-item border-0 mb-4">
                    <div class="card-header product-img position-relative 
                        overflow-hidden bg-transparent border p-0">
                        <img class="img-fluid w-100" 
                        src="img/product-1.jpg" alt="">
                    </div>
                    <div class="card-body border-left 
                    border-right text-center p-0 pt-4 pb-3">
                        <h6 class="text-truncate mb-3">
                            Colorful Stylish Shirt</h6>
                        <div class="d-flex justify-content-center">
                            <h6>R123.00</h6><
                            h6 class="text-muted ml-2">
                            <del>R123.00</del></h6>
                        </div>
                    </div>
                    <div class="card-footer d-flex 
                        justify-content-between bg-light border">
                        <a href="" class="btn btn-sm text-dark p-0">
                        
                        View Detail</a>
                        <a href="" class="btn btn-sm text-dark p-0 
                            add-to-cart-btn"
                           data-id="1"
                           data-product-name="Colorful Stylish Shirt"
                           data-product-image="img/product-1.jpg">
                            ^__i class="fas fa-shopping-cart 
                               text-primary mr-1">Add To Cart
                        </a>
                    </div>
                </div>
            </div>