Authentication in NodeJS involves verifying the identity of users accessing a web application or API endpoint. It typically involves processes such as user login, session management, and token-based authentication to ensure secure access to resources.

What is Authentication?

Authentication is the process of verifying the identity of a user or system. In the context of web development, authentication is commonly used to grant access to users based on their credentials, such as username and password.

Why Use Authentication?

Authentication is crucial for protecting sensitive information and restricting access to authorized users. By implementing authentication mechanisms, you can ensure that only authenticated users can access certain features or resources within your application.

Handle Authentication in NodeJS:

Authentication in NodeJS can be implemented using various techniques, including:

• Session-Based Authentication: In session-based authentication, the server creates a session for each authenticated user and stores session data on the server. This session data is used to validate subsequent requests from the user.
• Token-Based Authentication: Token-based authentication involves issuing a unique token to each authenticated user upon login. This token is then sent with subsequent requests as an authorization header or a cookie to authenticate the user.
• Middleware: Middleware functions can be used to enforce authentication and authorization rules for specific routes or endpoints in your application. These middleware functions can check for valid authentication tokens or session data before allowing access to protected resources.

const passport = require('passport');
const LocalStrategy = require('passport-local').Strategy;

passport.use(new LocalStrategy(
    (username, password, done) => {
        // Validate username and password
        // Example: Check against database
    }
));

app.post('/login', passport.authenticate('local'), (req, res) => {
    // Authentication successful
    res.send('Authentication successful');
});

function isAuthenticated(req, res, next) {
    if (req.isAuthenticated()) {
        return next();
    }
    res.status(401).send('Unauthorized');
}

app.get('/profile', isAuthenticated, (req, res) => {
    // Return user profile data
    res.send(req.user);
});