reduxjs toolkit – always give error “Unexpected token u in JSON at position 0” on rejected condition

i already take few hourse to solve this, but still not done yet. can somebody help me to solve this pls.

import { createSlice, createAsyncThunk, current } from ‘@reduxjs/toolkit’;
import axios from ‘axios’;

export const addToCart = createAsyncThunk(
  'cart/addCart',
  async (obj, thunkAPI) => {
    const response = await axios.get(
      `http://localhost:8000/api/products/${obj.id}`
    );
    const data = await response.data;
    thunkAPI.dispatch(
      cartAdd({
        product: data._id,
        name: data.name,
        image: data.image,
        price: data.price,
        countInStock: data.countInStock,
        qty: obj.qty,
      })
    );
    localStorage.setItem(
      'cartItems',
      JSON.stringify(thunkAPI.getState().cart.cartItems)
    );
  }
);

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

const cartSlice = createSlice({
  name: 'cart',
  initialState: {
    isLoading: false,
    cartItems: cartItemsFromStorage,
  },
  reducers: {
    cartAdd(state, { payload }) {
      const existItem = JSON.parse(JSON.stringify(state.cartItems)).find(
        (elem) => elem.product === payload.product
      );

      console.log(existItem);
      if (existItem) {
        return {
          ...state,
          cartItems: state.cartItems.map((x) =>
            x.product === payload.product ? payload : x
          ),
        };
      } else {
        return {
          ...state,
          cartItems: [...state.cartItems, payload],
        };
      }
    },
  },
  extraReducers: {
    [addToCart.pending]: (state, { payload }) => {
      state.isLoading = true;
    },
    [addToCart.fulfilled]: (state, action) => {
      state.isLoading = false;
      state.cartItems = action.payload;
    },
    [addToCart.rejected]: (state, action) => {
      console.log(action);
      state.isLoading = false;
    },
  },
});

the existing item give the result

{product: '628f92cfab7a84a5ab78fa3a', name: 'Airpods Wireless Bluetooth Headphones', image: '/images/airpods.jpg', price: 89.99, countInStock: 10, …}
countInStock: 10
image: "/images/airpods.jpg"
name: "Airpods Wireless Bluetooth Headphones"
price: 89.99
product: "628f92cfab7a84a5ab78fa3a"
qty: 1
[[Prototype]]: Object

but rejected condition always give this

"SyntaxError: Unexpected token u in JSON at position 0
    at JSON.parse (<anonymous>)
    at cartAdd (http://localhost:3000/static/js/bundle.js:932:30)
    at http://localhost:3000/static/js/bundle.js:3172:20
    at produce (http://localhost:3000/static/js/bundle.js:69721:15)
    at http://localhost:3000/static/js/bundle.js:3171:67
    at Array.reduce (<anonymous>)
    at reducer (http://localhost:3000/static/js/bundle.js:3147:25)
    at reducer (http://localhost:3000/static/js/bundle.js:3241:14)
    at combination (http://localhost:3000/static/js/bundle.js:63408:29)
    at k (<anonymous>:2235:16)"

can somebody help to get through this? thank you very much