Add JWT Authentication Middleware

Express.js

Node.js

Technical Specification

Add middleware that verifies a JWT from Authorization: Bearer <token>, decodes user, and attaches it to req.user.

Input/Output Samples

Input:GET /me with valid token

Output:{ id, email }

Optimal Logic Path

const jwt = require("jsonwebtoken");
const SECRET = process.env.JWT_SECRET || "dev-secret";

function authMiddleware(req, res, next) {
  const auth = req.header("authorization") || "";
  const [scheme, token] = auth.split(" ");
  if (scheme !== "Bearer" || !token) {
    return res.status(401).json({ error: "Unauthorized" });
  }
  try {
    const payload = jwt.verify(token, SECRET);
    req.user = payload;
    next();
  } catch (err) {
    return res.status(401).json({ error: "Invalid token" });
  }
}

app.get("/me", authMiddleware, (req, res) => {
  res.json({ user: req.user });
});

Architectural Deep-Dive

JWT auth is common for stateless APIs; we parse the header, verify token, and make payload available in req.user.