在Redux中添加项目数组之前，我如何检查项目是否不存在?

Question

我试图检查一个项目是否不在一个项目数组之前添加它，但我得到一个错误TypeError:无法读取未定义的属性(读取'indexOf')，请我在这里做错了，有人可以帮助我。

import { createSlice } from "@reduxjs/toolkit";
const initialState = {
items: [],
};
export const basketSlice = createSlice({
name: 'basket',
initialState,
reducers: {
addToBasket: (state, action) => {
let prevItems = state.items.indexOf(action.payload) > -1;
let newItems = [...state.items];
if (prevItems) {
newItems = newItems.filter((id) => id !== action.payload);
} else {
newItems.push(action.payload);
}
return {
...state.items,
newItems,
};
},
},
});
export const { addToBasket } = basketSlice.actions;
export const selectItems = (state) => state.basket.items;
export default basketSlice.reducer;

Answer 1

我认为问题出在你的return语句上。因为它用对象覆盖了整个状态。

return {
items: newItems
};

Answer 2

试试这个办法。

let items=['1','2','3']
let newItems=[];
if (!items.includes(action.payload) || items.length==0 ) {
// if item does not exists then add that item OR if items array is empty
const newArr = [...items,action.payload]
newItems.push(newArr);
} else {
// else return actual array
newItems = items;
}
return newItems;