NestJS Basic 4

Question 1

What is the purpose of Guards in NestJS?

Accepted Answer

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

Answer

Guards implement CanActivate and decide whether a request proceeds to the handler, making them ideal for authentication and authorization.

Question 2

Which interface must a NestJS Guard implement?

Accepted Answer

CanActivate

Answer

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

Question 3

What is an Interceptor in NestJS primarily used for?

Accepted Answer

Binding extra logic before/after method execution and transforming results

Answer

Interceptors wrap route handler execution, allowing you to add logging, transform responses, or handle errors around the handler call.

Question 4

In NestJS, which decorator is used to handle exceptions thrown within a controller?

Accepted Answer

@UseFilters()

Answer

@UseFilters() applies an exception filter to a controller or handler to catch and transform thrown exceptions.

Question 5

What does the @Query() decorator extract from a request?

Accepted Answer

Query string parameters (?key=value)

Answer

@Query() extracts query string parameters from the URL (e.g., /search?term=nestjs gives @Query('term') = 'nestjs').

NestJS Practice Test