Properly create error classes.

Useful utilities when creating custom error classes.

Features

- Ponyfill
error.cause
on
older Node.js and browsers
- Properly set error.name
- Fix issues when Error has been
polyfilled

Example

``js
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')
`

`js
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

`bash
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).

`js
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).

`js
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:

- Ends with the Error suffix
- Matches the
constructor's name
- Is
inherited
- Is
non-enumerable

`js
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

- modern-errors: Handle errors in
a simple, stable, consistent way
- error-custom-class: Create
one error class
- error-serializer: Convert
errors to/from plain objects
- normalize-exception:
Normalize exceptions/errors
- is-error-instance: Check if
a value is an Error instance
- merge-error-cause: Merge an
error with its cause
- set-error-class: Properly
update an error's class
- set-error-message: Properly
update an error's message
- wrap-error-message:
Properly wrap an error's message
- set-error-props: Properly
update an error's properties
- set-error-stack: Properly
update an error's stack
- error-cause-polyfill:
Polyfill error.cause
- handle-cli-error: 💣 Error
handler for CLI applications 💥
- log-process-errors: Show
some ❤ to Node.js process errors
- error-http-response:
Create HTTP error responses
- winston-error-format: Log
errors with Winston

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!