Custom typed errors in ES6

errors.js

// Hello. There is now a module for this.
// https://github.com/0x8890/error-class
// $ npm install error-class

const hasCaptureStackTrace = 'captureStackTrace' in Error

// Internal function to set up an error.
function setup (message) {
  const { constructor, constructor: { name } } = this

  if (hasCaptureStackTrace)
    Error.captureStackTrace(this, constructor)
  else
    Object.defineProperty(this, 'stack', {
      value: Error(message).stack
    })

  Object.defineProperties(this, {
    name: { value: name },
    message: { value: message }
  })
}

export class BadRequestError extends Error {
  constructor () { super(); setup.apply(this, arguments) }
}

export class UnauthorizedError extends Error {
  constructor () { super(); setup.apply(this, arguments) }
}

export class ForbiddenError extends Error {
  constructor () { super(); setup.apply(this, arguments) }
}

export class NotFoundError extends Error {
  constructor () { super(); setup.apply(this, arguments) }
}