kickstart-express/templates/add/auth/jwt/js/middleware/auth.js

A powerful CLI tool to quickly scaffold Express.js projects with modern tooling and best practices

import jwt from 'jsonwebtoken';

/**
 * JWT Authentication Middleware
 * Validates JWT tokens and attaches user information to the request
 */

export const authMiddleware = (req, res, next) => {
  try {
    // Get token from Authorization header
    const authHeader = req.headers.authorization;
    if (!authHeader || !authHeader.startsWith('Bearer ')) {
      return res.status(401).json({ 
        error: 'Access denied. No token provided or invalid format.' 
      });
    }

    const token = authHeader.substring(7); // Remove 'Bearer ' prefix

    // Verify token
    const decoded = jwt.verify(token, process.env.JWT_SECRET);
    // Attach user information to request
    req.user = decoded;
    next();
  } catch (error) {
    if (error instanceof jwt.TokenExpiredError) {
      return res.status(401).json({ error: 'Token has expired.' });
    }
    if (error instanceof jwt.JsonWebTokenError) {
      return res.status(401).json({ error: 'Invalid token.' });
    }
    return res.status(500).json({ error: 'Token verification failed.' });
  }
};