How can I implement middleware for authentication in Express?

How can I implement middleware for authentication in Express?

To implement middleware for authentication in Express, you can create a function that checks if a user is authenticated before allowing access to certain routes.

Can you show me a code example of that?

Sure! Here's a simple example:

function authMiddleware(req, res, next) {
    if (req.isAuthenticated()) {
        return next();
    }
    res.redirect('/login');
}

You can use this middleware in your routes like this:

app.get('/protected', authMiddleware, (req, res) => {
    res.send('This is a protected route!');
});

What if I want to use JWT for authentication?

If you're using JWT, you can modify the middleware to verify the token. Here's an example:

const jwt = require('jsonwebtoken');

function jwtMiddleware(req, res, next) {
    const token = req.headers['authorization'];
    if (!token) return res.sendStatus(403);

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