error-class-utils
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4.0.0 • Public • Published

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Properly create error classes.

Useful utilities when creating custom error classes.

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Features

Example

import {
  ensureCorrectClass,
  ponyfillCause,
  setErrorName,
} from 'error-class-utils'

export class CustomError extends Error {
  constructor(message, parameters) {
    super(message, parameters)

    // Fix some issues when `Error` has been polyfilled
    ensureCorrectClass(this, new.target)

    // Ponyfill `error.cause` on old Node.js/browsers
    ponyfillCause(this, parameters)
  }
}

// Properly set `error.name` as a non-enumerable and inherited property
setErrorName(CustomError, 'CustomError')
import { CustomError } from './errors.js'

const cause = new Error('innerMessage')
const error = new CustomError('message', { cause })
console.log(error instanceof CustomError) // true
console.log(error.name) // 'CustomError'
console.log(error.cause) // Error: innerMessage ...

Install

npm install error-class-utils

This package works in both Node.js >=18.18.0 and browsers.

This is an ES module. It must be loaded using an import or import() statement, not require(). If TypeScript is used, it must be configured to output ES modules, not CommonJS.

API

ensureCorrectClass(error, new.target)

error Error
new.target typeof Error
Return value: void

Some Error polyfills (such as es-shims/error-cause) prevent extending from it. This fixes it.

The second argument must be new.target. This must be called directly inside a class constructor, after super(message, parameters).

import { ensureCorrectClass } from 'error-class-utils'

class CustomError extends Error {
  constructor(message, parameters) {
    super(message, parameters)
    ensureCorrectClass(this, new.target)
  }
}

// Thanks to `ensureCorrectClass()`, this is now always true even when
// `Error` has been polyfilled
console.log(new CustomError('message') instanceof CustomError) // true

ponyfillCause(error, parameters?)

error Error
parameters ErrorParams?
Return value: void

Ponyfills error.cause on older Node.js and browsers.

This must be called inside a class constructor, after super(message, parameters).

import { ponyfillCause } from 'error-class-utils'

class CustomError extends Error {
  constructor(message, parameters) {
    super(message, parameters)
    ponyfillCause(this, parameters)
  }
}

try {
  throw new Error('innerMessage')
} catch (cause) {
  // Works on any platforms thanks to ponyfill
  const error = new CustomError('message', { cause })
  console.log(error.cause.message) // 'innerMessage'
}

setErrorName(ErrorClass, name)

ErrorClass typeof Error
name string
Return value: void

Set an ErrorClass's name.

This must be performed on an error class, not instance. Unlike setting this.name = '...' inside an error's constructor, this follows the native Error classes' pattern where error.name:

import { setErrorName } from 'error-class-utils'

class CustomError extends Error {}
setErrorName(CustomError, 'CustomError')

console.log(CustomError.name) // 'CustomError'
console.log(CustomError.prototype.name) // 'CustomError'

const error = new CustomError('message')
console.log(error.name) // 'CustomError'
console.log(Object.keys(error).includes('name')) // false

Related projects

Support

For any question, don't hesitate to submit an issue on GitHub.

Everyone is welcome regardless of personal background. We enforce a Code of conduct in order to promote a positive and inclusive environment.

Contributing

This project was made with ❤️. The simplest way to give back is by starring and sharing it online.

If the documentation is unclear or has a typo, please click on the page's Edit button (pencil icon) and suggest a correction.

If you would like to help us fix a bug or add a new feature, please check our guidelines. Pull requests are welcome!

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Install

npm i error-class-utils

Weekly Downloads

5,447

Version

4.0.0

License

MIT

Unpacked Size

18.4 kB

Total Files

11

Last publish

Collaborators

  • ehmicky