JWT authentication guard in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of a JWT authentication guard in NestJS?

A JWT authentication guard protects routes by checking if the incoming request has a valid JWT token. It ensures only authenticated users can access certain parts of the app.

intermediate

How does a JWT authentication guard verify a token in NestJS?

It extracts the token from the request header, then uses a JWT service to verify the token's signature and expiration. If valid, it allows access; otherwise, it denies it.

intermediate

Which NestJS interface must a JWT guard implement?

It must implement the CanActivate interface, which requires a canActivate method to decide if the request should proceed.

beginner

What happens if the JWT token is missing or invalid in a NestJS JWT guard?

The guard throws an UnauthorizedException, which stops the request and sends a 401 Unauthorized response to the client.

beginner

How do you apply a JWT authentication guard to a route in NestJS?

You use the @UseGuards() decorator on the controller or route handler and pass the JWT guard class to it.

What does a JWT authentication guard check in a NestJS app?

A If the database is connected

B If the user has admin rights

C If the request is from a mobile device

D If the request has a valid JWT token

A JWT authentication guard checks the presence and validity of a JWT token in the request.

Which method must a NestJS guard implement?

A canActivate

B handleRequest

C validateToken

D authenticate

The CanActivate interface requires the canActivate method to decide if a request can proceed.

Where is the JWT token usually found in an HTTP request for NestJS guards?

A URL query

B Authorization header

C Request body

D Cookies

JWT tokens are commonly sent in the Authorization header as a Bearer token.

What response status code does NestJS send if JWT guard denies access?

A 401 Unauthorized

B 403 Forbidden

C 404 Not Found

D 500 Internal Server Error

UnauthorizedException triggers a 401 Unauthorized response when access is denied.

How do you protect a NestJS route with a JWT guard?

A Set a route prefix

B Add a middleware function

C Use @UseGuards(JwtAuthGuard) decorator

D Use @Controller('jwt') decorator

The @UseGuards decorator applies the JWT guard to routes or controllers.

Explain how a JWT authentication guard works in NestJS to protect routes.

Think about the steps from receiving a request to deciding access.

Describe how to apply a JWT authentication guard to a NestJS controller or route.

Focus on the decorator usage in NestJS.