Session-based vs token-based auth in Node.js - Hands-On Comparison

Session-based vs Token-based Authentication in Node.js

📖 Scenario: You are building a simple Node.js server that handles user login. You want to understand how session-based and token-based authentication work by creating basic examples of each.

🎯 Goal: Build two simple authentication setups in Node.js: one using session-based authentication with express-session, and one using token-based authentication with JSON Web Tokens (jsonwebtoken).

📋 What You'll Learn

Create a user object with fixed username and password

Set up session configuration using express-session

Implement login route that creates a session on success

Set up token secret variable for JWT

Implement login route that returns a JWT token on success

Add middleware to protect a route using session or token

💡 Why This Matters

🌍 Real World

Web applications often need to authenticate users securely. Session-based auth stores login info on the server, while token-based auth uses tokens that clients keep. Understanding both helps build secure apps.

💼 Career

Many backend developer roles require knowledge of authentication methods. Knowing how to implement and protect routes with sessions and tokens is essential for building secure APIs and web apps.

1

Create a user object with fixed credentials

Create a constant called user with an object containing username set to 'user1' and password set to 'pass123'.

Node.js

# Your code here

Hint

Use const user = { username: 'user1', password: 'pass123' }; to create the user object.

2

Set up session configuration with express-session

Add these lines: import express and express-session, create an app using express(), and configure app to use express-session with a secret 'mysecret', resave set to false, and saveUninitialized set to true.

Node.js

const user = { username: 'user1', password: 'pass123' };
// Your code here

Hint

Use require to import modules and app.use(session({...})) to configure sessions.

3

Implement login route that creates a session on success

Add a POST route /login that reads username and password from req.body. If they match the user object, set req.session.user to user.username and send 'Logged in'. Otherwise, send 'Invalid credentials'. Use express.json() middleware.

Node.js

const user = { username: 'user1', password: 'pass123' };

const express = require('express');
const session = require('express-session');

const app = express();

app.use(session({
  secret: 'mysecret',
  resave: false,
  saveUninitialized: true
}));

// Your code here

Hint

Use app.post with express.json() to read JSON body and set session on success.

4

Set up token secret and implement token-based login route

Add jsonwebtoken import, create a constant tokenSecret with value 'tokensecret'. Add a POST route /token-login that reads username and password from req.body. If they match user, create a JWT token signed with tokenSecret containing { username } and send it as JSON { token }. Otherwise, send { error: 'Invalid credentials' }. Also add middleware authenticateToken that checks the token from Authorization header and calls next() if valid, else sends 401. Add a protected GET route /protected that uses authenticateToken and sends 'Protected content'.

Node.js

const user = { username: 'user1', password: 'pass123' };

const express = require('express');
const session = require('express-session');

const app = express();

app.use(express.json());
app.use(session({
  secret: 'mysecret',
  resave: false,
  saveUninitialized: true
}));

app.post('/login', (req, res) => {
  const { username, password } = req.body;
  if (username === user.username && password === user.password) {
    req.session.user = user.username;
    res.send('Logged in');
  } else {
    res.send('Invalid credentials');
  }
});

// Your code here

Hint

Use jsonwebtoken to create and verify tokens. Extract token from Authorization header. Protect routes with middleware.

Practice

1. Which of the following best describes session-based authentication in Node.js?

easy

A. User data is stored on the server and linked to the client via cookies.

B. User credentials are sent with every request without storing data on the server.

C. A signed token is stored on the server and sent to the client.

D. Authentication is done only once without any session or token.

Solution

1. Step 1: Understand session-based auth storage

   Session-based authentication stores user info on the server side, typically in memory or a database.

2. Step 2: Identify how client links to session

   The client receives a cookie that holds a session ID to link requests to the stored session data.

3. Final Answer:

   User data is stored on the server and linked to the client via cookies. -> Option A

4. Quick Check:

   Session-based auth = server stores data + cookie link [OK]

Hint: Session auth stores data server-side, linked by cookies [OK]

Common Mistakes:

• Thinking tokens are stored on the server in session auth
• Confusing session ID with user credentials
• Assuming session data is stored on the client

2. Which code snippet correctly sets a cookie for session-based authentication in Express.js?

easy

A. res.session('abc123');

B. res.setHeader('Authorization', 'Bearer abc123');

C. res.sendToken('abc123');

D. res.cookie('sessionId', 'abc123', { httpOnly: true });

Solution

1. Step 1: Identify Express.js method to set cookies

   Express uses res.cookie() to set cookies on the client with options like httpOnly for security.

2. Step 2: Match correct syntax for session cookie

   res.cookie('sessionId', 'abc123', { httpOnly: true }) correctly sets a cookie named 'sessionId'.

3. Final Answer:

   res.cookie('sessionId', 'abc123', { httpOnly: true }); -> Option D

4. Quick Check:

   Use res.cookie() to set session cookies [OK]

Hint: Use res.cookie() to set cookies in Express [OK]

Common Mistakes:

• Using res.setHeader for cookies instead of Authorization header
• Assuming res.sendToken is a valid Express method
• Trying to set session with res.session which doesn't exist

3. Given this token-based auth code snippet, what will be the output if the token is valid?

const jwt = require('jsonwebtoken');
const token = req.headers.authorization?.split(' ')[1];
try {
  const user = jwt.verify(token, 'secretKey');
  res.send(`User ID: ${user.id}`);
} catch {
  res.status(401).send('Unauthorized');
}

medium

A. SyntaxError

B. Unauthorized

C. User ID: [user's id from token]

D. Token string printed as is

Solution

1. Step 1: Extract token from Authorization header

   The code splits the 'Authorization' header to get the token part after 'Bearer'.

2. Step 2: Verify token and extract user info

   jwt.verify checks the token with 'secretKey' and returns the decoded user object if valid.

3. Final Answer:

   User ID: [user's id from token] -> Option C

4. Quick Check:

   Valid token returns decoded user info [OK]

Hint: Valid JWT returns decoded user info, else error [OK]

Common Mistakes:

• Assuming token is printed directly without decoding
• Confusing token verification failure with syntax error
• Ignoring optional chaining and possible undefined token

4. Identify the bug in this session-based auth middleware code snippet:

function auth(req, res, next) {
  if (!req.session.user) {
    res.status(401).send('Not logged in');
  }
  next();
}

medium

A. req.session.user should be req.user instead.

B. Missing return after sending 401 response causes next() to run anyway.

C. next() should be called before checking session.

D. res.status should be res.sendStatus.

Solution

1. Step 1: Analyze control flow after sending response

   After res.status(401).send(), the function continues and calls next(), allowing unauthorized access.

2. Step 2: Fix by adding return to stop execution

   Adding return before res.status stops the function, preventing next() from running when unauthorized.

3. Final Answer:

   Missing return after sending 401 response causes next() to run anyway. -> Option B

4. Quick Check:

   Return after response to stop middleware [OK]

Hint: Add return after res.send to prevent next() running [OK]

Common Mistakes:

• Calling next() before checking session
• Confusing req.session.user with req.user
• Using res.sendStatus instead of res.status().send()

5. You want to build a Node.js app that supports multiple devices per user and scales easily. Which authentication method is best and why?

hard

A. Token-based auth, because tokens are stateless and work well across devices.

B. Token-based auth, because it requires server to store session data.

C. Session-based auth, because cookies automatically sync across devices.

D. Session-based auth, because it stores user data on the server for security.

Solution

1. Step 1: Consider multi-device and scalability needs

   Supporting multiple devices means the server should not rely on storing session state for each device.

2. Step 2: Choose token-based auth for statelessness

   Token-based auth uses signed tokens stored client-side, allowing stateless servers and easy scaling.

3. Final Answer:

   Token-based auth, because tokens are stateless and work well across devices. -> Option A

4. Quick Check:

   Stateless tokens = scalable multi-device auth [OK]

Hint: Use token auth for scalable, multi-device apps [OK]

Common Mistakes:

• Thinking sessions sync automatically across devices
• Believing token auth requires server session storage
• Choosing session auth for scalability