Interceptor

ELI5 — The Vibe Check

An interceptor catches requests and responses on the way in and out, letting you transform them. It's like a translator at a meeting — they intercept what's said, modify it if needed, and pass it along. In NestJS, interceptors handle logging, caching, and response mapping.

Real Talk

An interceptor is a component that intercepts incoming requests or outgoing responses to add cross-cutting behavior. In NestJS, interceptors can transform responses, add extra logic before/after method execution, extend behavior with caching, and override exceptions. They wrap the execution stream using RxJS observables, enabling both pre- and post-processing.

Show Me The Code

@Injectable()
class LoggingInterceptor implements NestInterceptor {
  intercept(context: ExecutionContext, next: CallHandler) {
    const start = Date.now();
    return next.handle().pipe(
      tap(() => console.log(`${Date.now() - start}ms`))
    );
  }
}

When You'll Hear This

"Add a logging interceptor to measure response times on all endpoints." / "The transform interceptor wraps all responses in a standard { data, meta } format."