User Authentication with Context API and Hooks (useContext, useState)

App.js

import React from 'react';
import { BrowserRouter } from 'react-router-dom';

import { UserProvider } from './services/UserContext';

import Routes from './Routes'

function App() {
  return (
		<BrowserRouter>
			<UserProvider>
				<Routes />
			</UserProvider>
		</BrowserRouter>
  );
}

export default App;

AuthService.js

import api from './api';

export const login = async (username, password) => {
	const response = await api.post('login', {
		username,
		password
	});

	const token = response.data.token;
	if (token) {
		localStorage.setItem('user', JSON.stringify(response.data));
	}

	return response.data;
};

export const isAuthenticated = () => {
	const user = localStorage.getItem('user');
	if (!user) {
		return {}
	}
	return JSON.parse(user);
};

Dashboard.js

import React from 'react';

import Layout from '../../components/Layout';

const Dashboard = () => {
	return (
		<>
			<Layout>
				<h1>Dashboard</h1>
			</Layout>
		</>
	);
};

export default Dashboard;

Header.js

import React, { useContext } from 'react';
import { Link, useHistory } from 'react-router-dom';

import UserContext from '../../services/UserContext';

const Header = () => {
	const [ currentUser, setCurrentUser ] = useContext(UserContext);
	const history = useHistory();

	const handleLogOut = () => {
		localStorage.removeItem('user');
		setCurrentUser({});
		history.push('/');
	};

	console.log('header', currentUser);

	return (
		<>
			<header>
				<nav>
					<ul>
						<li>
							<Link to='/'>Home</Link>
						</li>
						<li>
							<Link to='/products'>Products</Link>
						</li>
						<li>
							<Link to='/users'>Users</Link>
						</li>
					</ul>
					<button
						type='button'
						onClick={handleLogOut}
					>
						Log out
					</button>
				</nav>
			</header>
		</>
	);
};

export default Header;

Layout.js

import React from 'react';
import Header from '../Header';

const Layout = ({ children }) => {
	return (
		<>
			<Header />
			{ children }
		</>
	);
};

export default Layout;

Login.js

import React, { useState } from 'react';
import { useHistory } from 'react-router-dom';

import { login } from '../../services/AuthService';


const Login = () => {
	const [ username, setUsername ] = useState('');
	const [ password, setPassword ] = useState('');
	const history = useHistory();

	const onChangeUsername = (e) => {
		setUsername(e.target.value);
	};

	const onChangePassword = (e) => {
		setPassword(e.target.value);
	};

	const onSubmit = async (e) => {
		e.preventDefault();
		try {
			await login(username, password);
			history.push('/admin');
		} catch (error) {
			console.error('error', error);
		}
	};

	return (
		<>
				<form onSubmit={onSubmit}>
					<label htmlFor='username'>Username</label>
					<input
						type='text'
						name='username'
						value={username}
						onChange={onChangeUsername}
					/>
					<label htmlFor='password'>Password</label>
					<input
						type='password'
						name='password'
						value={password}
						onChange={onChangePassword}
					/>
					<button type='submit'>Login</button>
				</form>
		</>
	);
};

export default Login;

Products.js

import React from 'react';

import Layout from '../../components/Layout';

const Products = () => {
	return (
		<>
			<Layout>
				<h1>Products</h1>
			</Layout>
		</>
	);
};

export default Products;

Routes.js

import React from 'react';
import { Switch, Route } from 'react-router-dom';

import Home from './pages/Home';
import Login from './components/Login';
import Dashboard from './components/Dashboard';
import Users from './components/Users';
import Products from './components/Products';

const Routes = () => {
	return (
		<Switch>
			<Route path='/' exact component={Home} />
			<Route path='/login' exact component={Login} />
			<Route path='/admin' component={Dashboard} />
			<Route path='/users' component={Users} />
			<Route path='/products' component={Products} />
		</Switch>
	);
};

export default Routes;

UserContext.js

import React, { useState, useEffect, createContext } from 'react';
import { Redirect } from 'react-router-dom';
import { isAuthenticated } from './AuthService';

import Login from '../components/Login';

const UserContext = createContext();

export const UserProvider = ({ children }) => {
	const [ currentUser, setCurrentUser ] = useState(undefined);

	useEffect(() => {
		const checkLoggedIn = async () => {
			let cuser = isAuthenticated();
			if (cuser === null) {
				localStorage.setItem('user', '');
				cuser = '';
			}

			setCurrentUser(cuser);
		};

		checkLoggedIn();
	}, []);

	console.log('usercontext', currentUser);

	return (
		<UserContext.Provider value={[currentUser, setCurrentUser]}>
			{ currentUser?.token ? children : <Login />}
		</UserContext.Provider>
	);
};


export default UserContext;

Users.js

import React from 'react';

import Layout from '../../components/Layout';

const Users = () => {
	return (
		<>
			<Layout>
				<h1>Users</h1>
			</Layout>
		</>
	);
};

export default Users;

what is localStorage and how it is defined ?

what is localStorage and how it is defined ?

It saves the data in the browser

for saving: localStorage.setItem('key_name', data_to_save);
for getting the saved data: localStorage.getItem('key_name');