How do you create a domain-specific custom exception class in NestJS?

Q: How do you create a domain-specific custom exception class in NestJS?

// Extending built-in exceptions — status is already set export class UserNotFoundException extends NotFoundException { constructor(userId: number | string) { super(`User #${userId} was not found`); } } export class EmailAlreadyExistsException extends ConflictException { constructor(email: string) { super(`The email '${email}' is already registered`); } } // Extending HttpException directly — full control over status and body export class BusinessRuleException extends HttpException { constructor(rule: string, details?: Record ) { super( { statusCode: 422, message: `Business rule violated: ${rule}`, details }, HttpStatus.UNPROCESSABLE_ENTITY, ); } } // Usage — clean, self-documenting call sites throw new UserNotFoundException(userId); throw new EmailAlreadyExistsException(dto.email); throw new BusinessRuleException('Order total must exceed minimum', { minimum: 10 }); Call sites are clean — no magic strings or repeated status codes across the codebase. Extending the right subclass makes the HTTP semantic obvious to code reviewers. A single place to change the message format or add logging logic for that error type. Filters can catch domain exceptions by type: @Catch(UserNotFoundException). Extend HttpException directly when no built-in subclass captures the right semantic.

Difficulty: 5/10

custom exception class, exception filters, error handling

Extend one of the built-in exceptions or HttpException directly. Hard-code the status and default message in the constructor so call sites remain clean and self-documenting. Extending the right HTTP semantic subclass (NotFoundException, ConflictException, etc.) makes the intent obvious.

Domain-specific exception classes

Benefits of domain-specific exception classes:

1
Call sites are clean — no magic strings or repeated status codes across the codebase.
2

How do you create a domain-specific custom exception class in NestJS?

Difficulty: 5/10

custom exception class, exception filters, error handling

Extend one of the built-in exceptions or HttpException directly. Hard-code the status and default message in the constructor so call sites remain clean and self-documenting. Extending the right HTTP semantic subclass (NotFoundException, ConflictException, etc.) makes the intent obvious.

Domain-specific exception classes

Benefits of domain-specific exception classes:

1
Call sites are clean — no magic strings or repeated status codes across the codebase.
2

How do you create a domain-specific custom exception class in NestJS?

Extend one of the built-in exceptions or HttpException directly. Hard-code the status and default message in the constructor so call sites remain clean and self-documenting. Extending the right HTTP semantic subclass (NotFoundException, ConflictException, etc.) makes the intent obvious.

How do you create a domain-specific custom exception class in NestJS?

Extend one of the built-in exceptions or HttpException directly. Hard-code the status and default message in the constructor so call sites remain clean and self-documenting. Extending the right HTTP semantic subclass (NotFoundException, ConflictException, etc.) makes the intent obvious.

Scenario Questions

Follow-up Questions