Implement JWT Authentication in Node.js and Express

Use this AI prompt to generate complete JWT authentication for Node.js with login, signup, and middleware-based token verification for protected routes.

🧠 What This Prompt Does

This AI prompt helps you create a JWT-based authentication system for Node.js using Express.
It includes signup/login endpoints, token generation, and middleware for route protection.

💬 The Prompt

You are a backend developer.
Generate a JWT authentication system in Node.js using Express.

Requirements:

- Signup and login routes
- Generate JWT tokens using jsonwebtoken
- Middleware to verify tokens
- Return proper error codes for unauthorized requests

🚀 Example Output (AI Generated)

import express from 'express';
import jwt from 'jsonwebtoken';
import bcrypt from 'bcryptjs';

const app = express();
app.use(express.json());

const users = [];
const SECRET = 'mysecretkey';

// Signup route
app.post('/signup', async (req, res) => {
  const { email, password } = req.body;
  const hash = await bcrypt.hash(password, 10);
  users.push({ email, password: hash });
  res.status(201).json({ message: 'User created' });
});

// Login route
app.post('/login', async (req, res) => {
  const { email, password } = req.body;
  const user = users.find((u) => u.email === email);
  if (!user || !(await bcrypt.compare(password, user.password))) {
    return res.status(401).json({ error: 'Invalid credentials' });
  }
  const token = jwt.sign({ email }, SECRET, { expiresIn: '1h' });
  res.json({ token });
});

// Auth middleware
const verifyToken = (req, res, next) => {
  const auth = req.headers.authorization;
  if (!auth) return res.status(401).json({ error: 'No token provided' });
  try {
    req.user = jwt.verify(auth.split(' ')[1], SECRET);
    next();
  } catch {
    res.status(401).json({ error: 'Invalid token' });
  }
};

// Protected route
app.get('/profile', verifyToken, (req, res) => {
  res.json({ email: req.user.email });
});

📘 When to Use This Prompt

• When building secure login flows in Node.js.
• For APIs requiring authenticated user access.
• When replacing session-based authentication with tokens.

💡 Best Practices

• Store tokens securely (prefer httpOnly cookies).
• Use refresh tokens for long-lived sessions.
• Always validate token expiry on the backend.
• Rotate JWT secrets periodically for added security.

🏁 Summary

This prompt generates a complete JWT authentication setup for Express, helping you secure your backend APIs efficiently and cleanly.