未处理的拒绝 (TypeError)：state.cartItems 未定义

Question

我正在关注 MERN STACK 教程并设置我的购物车这是我收到的错误，但是，我 console.log 我的减速器中的数据正在显示，但不知道为什么会显示此错误

Unhandled Rejection (TypeError): state.cartItems is undefined

还有，为什么导师用localStorage来存储数据，我们不能在抓取Cart Action后直接发送给reducer吗... 有什么关系

谢谢

购物车操作

import { ADD_TO_CART } from '../constants/CartConstants';
import axios from "axios";

export const addToCart = (id, qty) => async (dispatch, getState) => {

    const { data } = await axios.get(`/api/products/${id}`);

    dispatch({
        type: ADD_TO_CART,
        payload: {
            product: data._id,
            name: data.name,
            image: data.image,
            price: data.price,
            countInStock: data.countInStock,
            qty
        }

    })

    localStorage.setItem('cartItems', JSON.stringify(getState().cart.cartItems))

商店

import {createStore , applyMiddleware, combineReducers} from 'redux';
import thunk from 'redux-thunk'
import {composeWithDevTools} from 'redux-devtools-extension';
import {productListReducer , productDetailsReducer } from './reducers/productReducer' ;
import {cartReducer} from "./reducers/cartReducer"

const reducer = combineReducers({
    productList: productListReducer,
    productDetails:productDetailsReducer,
    cart: cartReducer
});

const cartItemsFromStorage = localStorage.getItem('cartItems') ? JSON.parse(localStorage.getItem('cartItems')) : []

const initialState = {
    cart: cartItemsFromStorage
};

const middleware = [thunk];
const store = createStore(reducer , initialState ,   composeWithDevTools(applyMiddleware(...middleware)))

//composite with dev tools is used to connect our store with our devtools

export default store;

推车减速机

import { ADD_TO_CART } from '../constants/CartConstants';

export const cartReducer = (state = { cartItems: [] }, action) => {
    switch (action.type) {
        case ADD_TO_CART:
            const item = action.payload;
            const existItem = state.cartItems.find((x) => x.product === item.product)
            console.log(existItem)

            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
    }
}

Answer 1

确保这符合您的状态结构

localStorage.setItem('cartItems', JSON.stringify(getState().*cart.cartItems*))

如果您命名不同，它可能会改变，例如

cartReducer.cartItems

Answer 2

我知道这是一个老问题，但如果有人遇到同样的问题，答案是

替换这个：

const initialState = {cart: cartItemsFromStorage};

有了这个：

const initialState = { cart: { cartItems: cartItemsFromStorage } };

在store.js

未处理的拒绝 (TypeError)：state.cartItems 未定义

Unhandled Rejection (TypeError): state.cartItems is undefined

javascript

frontend

reactjs

react-redux

mern