问使用本地存储的Logot函数

EN

import React from "react";
const UserContext = React.createContext();

function getUserFromLocalStorage() {
    return localStorage.getItem("authToken")
      ? JSON.parse(localStorage.getItem("authToken"))
      : { username: null, token: null };
  }

function UserProvider({ children }) {
  const [user, setUser] = React.useState(getUserFromLocalStorage());
  
    const history = useHistory();
    const logoutHandler = () =>{
      localStorage.removeItem("user");
      history.push("/")
  }
  return (
    <UserContext.Provider
      value={{ user, logoutHandler  }}
    >
      {children}
    </UserContext.Provider>
  );
}

export { UserContext, UserProvider };

import { useState, } from "react";
import { useHistory } from "react-router-dom"
import axios from "axios";
import { Link } from "react-router-dom";
import "./Signin.css";

const Login = () => {
  const { user, setUser } = React.useContext(UserContext);
  const [email, setEmail] = useState("");
  const [password, setPassword] = useState("");
  const [error, setError] = useState("");
  const history = useHistory()

  
  const loginHandler = async (e) => {
    e.preventDefault();
    const config = {
      header: {
        "Content-Type": "application/json",
      },
    };

    try {
      const { data } = await axios.post(
        "http://localhost:5000/api/auth/login",
        { email, password },
        config
      );

      localStorage.setItem("authToken", data.token);
      setUser(user)
      history.push("/");
    } catch (error) {
      if (error.response) {
        setError(error.response.data.error);
      }
      setTimeout(() => {
         setError("");
      }, 5000);
    }
  };

  return (
    <div className="login-screen">
      <form onSubmit={loginHandler} className="login-screen__form">
        <h3 className="login-screen__title">Login</h3>
        {error && <span className="error-message">{error}</span>}
        <div className="form-group">
          <label htmlFor="email">Email:</label>
          <input
            type="email"
            required
            id="email"
            placeholder="Email address"
            onChange={(e) => setEmail(e.target.value)}
            value={email}
            tabIndex={1}
          />
        </div>
        <div className="form-group">
          <label htmlFor="password">
            Password:{" "}
            <Link to="/forgotpassword" className="login-screen__forgotpassword">
              Forgot Password?
            </Link>
          </label>
          <input
            type="password"
            required
            id="password"
            autoComplete="true"
            placeholder="Enter password"
            onChange={(e) => setPassword(e.target.value)}
            value={password}
            tabIndex={2}
          />
        </div>
        <button type="submit" className="btn btn-primary">
          Login
        </button>

        <span className="login-screen__subtext">
          Don't have an account? <Link to="/register">Register</Link>
        </span>
      </form>
    </div>
  );
};

export default Login;

import React from 'react';
import { Link, useHistory } from "react-router-dom";
import Search from './Search';
import './Header.css'
import SearchBooks from './SearchBooks';
import LoginLink from '../Signin/LoginLink';
import CartLink from '../Cart/CartLink';
import { UserContext } from '../../context/user';

const Header = () => {
const { user } = React.useContext(UserContext);

    return (
        <div className='header__container'>
            <Link to='/'>
            <img src='/audi.png' />
            </Link>  
            <li>
              <LoginLink />
            </li>
           {user.authToken &&(
            <CartLink /> 
           )    
           }      
        </div>
    )
}

import React from "react";
import { Link } from "react-router-dom";
import { UserContext } from "../../context/user";
import { useHistory } from "react-router-dom"
export default function LoginLink() {

  const { user, logoutHandler } = React.useContext(UserContext);

  if (user.authToken) {
    return (
      <button
        onClick={() => {
          logoutHandler();
        }}
        className="login-btn"
      >
        logout
      </button>
    );
  }
  return <Link to="/login">login</Link>;
}