Questions
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1What built-in HTTP exceptions does NestJS provide out of the box?
2What interface must an exception filter implement and what are the two parameters of catch()?
3How do you apply an exception filter at the method, controller, and global level in NestJS?
4How do you add custom response headers or set cookies inside an exception filter in NestJS?
5How do you unit test an exception filter in NestJS?
6How do you implement a filter that adds a request correlation ID to every error response in NestJS?
7How do getResponse() and getStatus() work on an HttpException and what can getResponse() return?
8How do you create a domain-specific custom exception class in NestJS?
9How does exception filter resolution order work when multiple filters are registered at different levels in NestJS?
10How do you register multiple global filters that each handle a different exception type in NestJS?
11What does the @Catch() decorator do and what happens when you omit its argument?
12How do you extend the built-in BaseExceptionFilter to add logging while keeping default NestJS behaviour?
13How do you handle exceptions differently in a filter depending on whether the request is HTTP, WebSocket, or RPC?
14What are the two ways to register a global exception filter in NestJS and what is the key difference?
15How do interceptors and exception filters divide error-handling responsibility in NestJS?
16How do you write an exception filter that handles GraphQL errors differently from REST errors in NestJS?
17How do you prevent sensitive information from leaking through exception responses in production NestJS apps?
18How do you handle async operations inside an exception filter in NestJS, for example logging to a database?
19What is HttpException in NestJS and what two arguments does its constructor take?
20What does NestJS's built-in global exception layer do when no custom filter is registered?
21What is the cause option on HttpException and how should you use it for error tracing?
22How do you write a production-ready global all-exceptions filter that handles HttpException and unexpected errors differently?
23How do you integrate a third-party error tracker like Sentry inside a global exception filter in NestJS?
24How do you map database and ORM exceptions to HTTP exceptions using a global filter in NestJS?
25How do you re-throw an exception from within a filter to let a higher-scoped filter handle it in NestJS?
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How do you handle exceptions differently in a filter depending on whether the request is HTTP, WebSocket, or RPC?

Use host.getType() to detect the transport and branch accordingly. Each transport has its own error format: HTTP uses res.status().json(), WebSocket emits an error event to the socket client, and RPC returns a throwError observable. Throw the transport-appropriate exception in each branch.

Universal exception filter across transports
Transport-specific error handling:
  1. 1

    HTTP — use host.switchToHttp().getResponse().status().json() for standard REST error responses.

  2. 2

    WebSocket — use host.switchToWs().getClient().emit('exception', ...) to send the error to the socket.

  3. 3

    RPC — return a throwError() observable; the microservice framework handles serialization.

  4. 4

    WsException from @nestjs/websockets should be thrown in WebSocket context for proper formatting.

  5. 5

    A single filter registered globally can handle all transports by branching on host.getType().