Exception filters in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of an Exception Filter in NestJS?

An Exception Filter in NestJS catches errors thrown during request handling and allows you to control the response sent back to the client, improving error management.

beginner

How do you create a custom Exception Filter in NestJS?

You create a class that implements the <code>ExceptionFilter</code> interface and define a <code>catch()</code> method to handle exceptions and send custom responses.

beginner

Which decorator is used to bind an Exception Filter to a controller or route in NestJS?

The @UseFilters() decorator is used to apply an Exception Filter to a controller or specific route handler.

intermediate

What is the role of the ArgumentsHost parameter in the catch() method of an Exception Filter?

ArgumentsHost provides access to the underlying platform's request and response objects, allowing you to customize the error response based on the context (HTTP, WebSocket, etc.).

intermediate

Can Exception Filters in NestJS handle both synchronous and asynchronous exceptions?

Yes, Exception Filters can catch exceptions thrown synchronously or asynchronously during request processing, making error handling consistent.

Which interface must a custom Exception Filter implement in NestJS?

A FilterInterface

B ErrorHandler

C Catchable

D ExceptionFilter

Custom Exception Filters must implement the ExceptionFilter interface to define the catch() method.

What decorator applies an Exception Filter to a specific route or controller?

A @UseFilters()

B @HandleError()

C @Exception()

D @Catch()

@UseFilters() binds Exception Filters to controllers or routes.

What does the catch() method receive as arguments?

A Request and Response objects

B Exception object and ArgumentsHost

C Only the Exception object

D Only the ArgumentsHost

The catch() method receives the thrown exception and an ArgumentsHost to access request/response.

Which of these is NOT a typical use of Exception Filters?

A Handling database migrations

B Logging errors

C Transforming error responses

D Sending custom HTTP status codes

Exception Filters do not handle database migrations; they focus on error handling.

Can Exception Filters handle exceptions from asynchronous code in NestJS?

A Only exceptions from Promises

B No, only synchronous exceptions

C Yes, they handle both sync and async exceptions

D Only exceptions from Observables

Exception Filters catch exceptions thrown synchronously or asynchronously.

Explain how to create and apply a custom Exception Filter in NestJS.

Think about the class, method, and decorator involved.

Describe the benefits of using Exception Filters in a NestJS application.

Consider how filters improve error management and user experience.