未处理的拒绝（TypeError）：无法读取 null 的属性“产品”

Question

运行代码时出错：

export const cartReducer = (state = {cartItems:[]}, action) => {
    switch (action.type){
        case CART_ADD_ITEM:
            const item = action.payload;
            const existItem = state.cartItems.find((x) => x.product === item.product );
            if(existItem){
                return{
                    ...state,
                    cartItems: state.cartItems.map((x)=>
                    x.product === existItem.product ? item:x),
                };
            }else{
                return{...state, cartItems:[...state.cartItems, item]};
            }
            default:
                return state;
    }
};


export const addToCart = (productId, qty) =>async (dispatch, getState) =>{
    const {data} = await Axios.get(`/api/products/${productId}`);
    dispatch({
        type: CART_ADD_ITEM,
        payload: {
            name: data.name,
            image: data.image,
            price: data.price,
            countInStock: data.countInStock,
            product: data._id,
            qty,
        },
    });
    localStorage.setItem('cartItems', JSON.stringify(getState().cart.cartItems));
};

Answer 1

你应该看看你的item 常量，它来自action.payload。看来它的内容可能是空的。这将使它在find 内调用item.product 导致 cannot read property 'product' of null 错误。