JWT token verification middleware in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of JWT token verification middleware in an Express app?

It checks if the incoming request has a valid JWT token to allow access to protected routes.

beginner

Which HTTP header usually carries the JWT token in requests?

The 'Authorization' header, often with the format 'Bearer <token>'.

beginner

What happens if the JWT token is missing or invalid in the verification middleware?

The middleware sends a 401 Unauthorized response and stops the request from reaching protected routes.

intermediate

How does the middleware verify the JWT token?

It uses a secret key or public key to decode and check the token's signature and expiration.

intermediate

Why is it important to place JWT verification middleware before protected route handlers?

So that only requests with valid tokens can access those routes, protecting sensitive data or actions.

Which Express middleware function is best for verifying JWT tokens?

A A function that reads the Authorization header and checks the token

B A function that logs request times

C A function that serves static files

D A function that parses JSON bodies

JWT verification middleware reads the Authorization header to check the token's validity.

What status code should the middleware return if the JWT token is invalid?

A 200 OK

B 404 Not Found

C 401 Unauthorized

D 500 Internal Server Error

401 Unauthorized indicates the client is not authorized due to invalid or missing credentials.

Where is the JWT token usually stored on the client side for sending with requests?

A In the server memory

B In the URL path

C In the request body

D In a cookie or local storage

Clients often store JWT tokens in cookies or local storage to send them in Authorization headers.

Which library is commonly used in Express apps to verify JWT tokens?

A jsonwebtoken

B express-session

C cors

D body-parser

The 'jsonwebtoken' library provides functions to sign and verify JWT tokens.

What does the 'Bearer' keyword in the Authorization header mean?

A It is a cookie name

B It indicates the token type is a bearer token

C It is a password

D It is a username

'Bearer' means the token is a bearer token, which grants access to the bearer.

Explain how JWT token verification middleware works in an Express app.

Think about the steps from receiving a request to deciding if it can access protected routes.

Describe why JWT token verification middleware is important for securing Express routes.

Consider what could happen if you skip token checks on protected routes.