NestJS NestJS 2

Question 1

Which decorator is used to define a NestJS middleware class?

Accepted Answer

@Injectable()

Answer

NestJS middleware classes are decorated with @Injectable() and must implement the NestMiddleware interface.

Question 2

How do you apply middleware to specific routes in a NestJS module?

Accepted Answer

Configuring it in the configure() method of the module class

Answer

NestJS modules implement the NestModule interface and use the configure() method with MiddlewareConsumer to apply middleware to routes.

Question 3

What is the purpose of a NestJS Guard?

Accepted Answer

To determine whether a request should be handled by the route handler

Answer

Guards implement the CanActivate interface and decide whether a given request will be handled by the route handler, typically used for authorization.

Question 4

Which interface must a NestJS Guard implement?

Accepted Answer

CanActivate

Answer

NestJS Guards must implement the CanActivate interface, which requires a canActivate() method returning a boolean or Observable<boolean>.

Question 5

What does the @Roles() decorator typically represent in NestJS?

Accepted Answer

A custom metadata decorator used with Guards for role-based access control

Answer

@Roles() is a custom metadata decorator created using SetMetadata() that stores role data, which Guards then read via the Reflector service.

NestJS Practice Test