Create an express server that has an authorised endpoint using the JWT library.

const express = require('express');
const jwt = require('jsonwebtoken');

const app = express();
const PORT = 3000;
const SECRET_KEY = 'secret';

app.use(express.json());


app.post('/login', (req, res) => {
  const { username, password } = req.body;

  if (username === 'user' && password === '123') {
    const token = jwt.sign({ username }, SECRET_KEY);
    res.json({ token });
  } else {
    res.status(401).json({ message: 'Invalid credentials' });
  }
});


function auth(req, res, next) {
  const token = req.headers.authorization?.split(' ')[1];
  if (!token) return res.sendStatus(401);

  jwt.verify(token, SECRET_KEY, (err, user) => {
    if (err) return res.sendStatus(403);
    req.user = user;
    next();
  });
}


app.get('/protected', auth, (req, res) => {
  res.json({ message: 'Welcome!', user: req.user });
});

app.listen(PORT, () => {
  console.log(`Server running on http://localhost:${PORT}`);
});

npm init -y
npm install express jsonwebtoken body-parser