Custom error class in TypeScript

I'd like to create my own error class in TypeScript, extending core Error to provide better error handling and customized reporting. For example, I want to create an HttpRequestError class with url, response and body passed into its constructor, which reponds with Http request to http://example.com failed with status code 500 and message: Something went wrong and proper stack trace.

How to extend core Error class in TypeScript? I've already found post in SO: https://stackoverflow.com/questions/12915412/how-do-i-extend-a-host-object-e-g-error-in-typescript but this solution doesn't work for me. I use TypeScript 1.5.3

Any ideas?

TypeScript 2.1 had a breaking changes regarding Extending built-ins like Error.

From the TypeScript breaking changes documentation

class FooError extends Error {
    constructor(msg: string) {
        super(msg);

        // Set the prototype explicitly.
        Object.setPrototypeOf(this, FooError.prototype);
    }

    sayHello() {
        return "hello " + this.message;
    }
}

Then you can use:

let error = new FooError("Something really bad went wrong");
if(error instanceof FooError){
   console.log(error.sayHello());
}

Until 1.6 rolls around, I've just been making my own extendable classes.

class BaseError {
	constructor () {
		Error.apply(this, arguments);
	}
}

BaseError.prototype = new Error();

class HttpRequestError extends BaseError {
	constructor (public status: number, public message: string) {
		super();	
	}
}

var error = new HttpRequestError(500, 'Server Error');

console.log(
	error,
	// True
	error instanceof HttpRequestError,
	// True
	error instanceof Error
);

I am using TypeScript 1.8 and this is how I use custom error classes:

UnexpectedInput.ts

class UnexpectedInput extends Error {

  public static UNSUPPORTED_TYPE: string = "Please provide a 'String', 'Uint8Array' or 'Array'.";

  constructor(public message?: string) {
    super(message);
    this.name = "UnexpectedInput";
    this.stack = (<any> new Error()).stack;
  }

}

export default UnexpectedInput;

MyApp.ts

import UnexpectedInput from "./UnexpectedInput";

...

throw new UnexpectedInput(UnexpectedInput.UNSUPPORTED_TYPE);

For TypeScript versions older than 1.8, you need to declare Error:

export declare class Error {
  public message: string;
  public name: string;
  public stack: string;
  constructor(message?: string);
}

For Typescript 3.7.5 this code provided a custom error class that also captured the correct stack information. Note instanceof does not work so I use name instead

// based on https://gunargessner.com/subclassing-exception

// example usage
try {
  throw new DataError('Boom')
} catch(error) {
  console.log(error.name === 'DataError') // true
  console.log(error instanceof DataError) // false
  console.log(error instanceof Error) // true
}

class DataError {
  constructor(message: string) {
    const error = Error(message);

    // set immutable object properties
    Object.defineProperty(error, 'message', {
      get() {
        return message;
      }
    });
    Object.defineProperty(error, 'name', {
      get() {
        return 'DataError';
      }
    });
    // capture where error occured
    Error.captureStackTrace(error, DataError);
    return error;
  }
}

There are some other alternatives and a discussion of the reasons.

There is a neat library for this at https://www.npmjs.com/package/ts-custom-error

ts-custom-error allow you to create error custom Error very easily:

import { CustomError } from 'ts-custom-error'
 
class HttpError extends CustomError {
    public constructor(
        public code: number,
        message?: string,
    ) {
        super(message)
    }
}

usage:

new HttpError(404, 'Not found')