我初始化对象和数组的方式是否有问题。 我试图将购物车数据保存到 localStorage 中。我从状态中获取数据，并在控制台中显示。登录后，对象似乎可以工作，但数组不行，我不明白代码出了什么问题。

未处理的拒绝 (TypeError)：cartItemObjectArray.push 不是函数

编辑：但是，即使本地存储未定义，if 语句似乎也认为它不是未定义的，我也不知道如何解决它。

下面是我的构造函数

constructor(props) {
    super(props);
    this.state = {
      comicId: null,
      selectedOption: null,
      comicPrice: null,
      purchaseType: null,
      priceCurrency: "$",
      currencyVisibility: null,
      issueObjectState: null,
      seriesObjectState: null,
      pricingObjectState: null,
    };
  }

下面是我的 onSubmit()，这样每当用户点击添加到购物车时，都会检索和设置状态值

onSubmit = async (event) => {
    //submit function when adding item to cart

    if (localStorage.getItem("cartitem") != undefined) {
      //if there are items in the array then do this
      console.log("It came not undefined");
      let cartItemObjectArray = localStorage.getItem("cartitem");
      let cartItemObject = {
        comicid: this.state.comicId,
        purchasetype: this.state.purchaseType,
      };
      console.log(cartItemObject);
      cartItemObjectArray.push(cartItemObject);
      localStorage.setItem("cartitem", cartItemObjectArray);
      toast.success("Item Added to cart");
      console.log("This is the mighty array ", cartItemObjectArray);
    } else {
      //if there are no items in the cart array in the local storage then initialize and do this
      console.log("It came undefined");
      let cartItemObjectArray = [];
      let cartItemObject = {
        comicid: this.state.comicId,
        purchasetype: this.state.purchaseType,
      };
      console.log(cartItemObject);
      cartItemObjectArray.push(cartItemObject);
      localStorage.setItem("cartitem", cartItemObjectArray);
      toast.success("Item Added to cart");
      console.log("This is the mighty array ", cartItemObjectArray);
    }

else if (cartItemFromLocalStorage == null) {
      //if there are no items in the cart array in the local storage then initialize and do this
      console.log("It came undefined");
      let cartItemObjectArray = [];
      let cartItemObject = {
        comicid: this.state.comicId,
        purchasetype: this.state.purchaseType,
      };
      console.log(cartItemObject);
      cartItemObjectArray.push(cartItemObject);
      localStorage.setItem("cartitem", JSON.stringify(cartItemObjectArray));
      toast.success("Item Added to cart");
      console.log("This is the mighty array ", cartItemObjectArray);
    }
  };