NestJS Exception Factory

Simple Factory Function to create NestJS Exceptions.

Code

declare class CustomExceptionProtoType extends HttpException {
  constructor();
}

export function createException(
  status: HttpStatus,
  errorCode: string,
  message: string
) {
  class CustomException extends HttpException {
    constructor() {
      super({ status, errorCode, message }, status);
      Object.setPrototypeOf(this, Object.getPrototypeOf(HttpException));
    }
  }
  return CustomException as unknown as typeof CustomExceptionProtoType;
}

Usage

Copy & Paste into your nestjs project. Then use it like this:

export const CustomException = createException(
  HttpStatus.BAD_REQUEST,
  'CUSTOM_ERROR_CODE',
  'Custom Error Message'
);

function someFunction() {
  ...
  throw new CustomException();
  ...
}

Warning

Do not import this code as a module.

It will not work.

Becasue behaviour of instanceof operator, is that the class must be exactly in the parent chain, in the sense of JavaScript object reference. Hence, if you import HttpException class twice, they are different actual object references, and instanceof may give a "false" negative.

In NestJS, checking exception type is done by instanceof operator. So, if you import this code as a module, it will not work.