set-error-props

Properly update an error's properties.

Features

• Prevents overriding error core properties (name, message, etc.)
• Protects against prototype pollution
• Prevents overriding existing properties
• Copies another error's properties
• Can set properties as non-enumerable
• Preserves properties descriptors (enumerable, writable, configurable, get/set)
• Exception-safe: this only throws syntax errors
• Strict TypeScript typing of the return value

Example

import setErrorProps from 'set-error-props'

const error = new Error('one')
setErrorProps(error, { prop: true, message: 'two' })
console.log(error.prop) // true
console.log(error.message) // 'one': message is readonly

Install

npm install set-error-props

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

setErrorProps(error, props, options?)

error Error | object
props Error | object
options Options?
Return value: Error

Assigns props to error, then returns error.

Options

soft

Type: boolean
Default: false

Prevents overriding existing properties.

Usage

Error core properties

const error = new Error('one')
setErrorProps(error, { message: 'two' })
console.log(error.message) // 'one'

Prototype pollution

const error = new Error('one')
setErrorProps(error, { toString: () => 'injected' })
console.log(error.toString()) // 'Error: one'
console.log(Error.prototype.toString()) // 'Error'

Overriding protection

const error = new Error('message')
error.one = true
setErrorProps(error, { one: false, two: true }, { soft: true })
console.log(error.one) // true
console.log(error.two) // true

Error copy

const error = new Error('one')
const secondError = new Error('two')
secondError.prop = true
setErrorProps(error, secondError)
console.log(error.message) // 'one'
console.log(error.prop) // true

Non-enumerable properties

const error = new Error('message')

// Properties that start with `_` are not enumerable
setErrorProps(error, { _one: true, two: true })

console.log(error._one) // true
console.log(error.two) // true
console.log(Object.keys(error)) // ['two']
console.log(error) // Prints `two` but not `_one`

Descriptors

const error = new Error('message')
Object.defineProperty(error, 'prop', {
  value: false,
  enumerable: false,
  writable: true,
  configurable: true,
})
setErrorProps(error, { prop: true })
console.log(error.prop) // true
console.log(Object.getOwnPropertyDescriptor(error, 'prop').enumerable) // false

Exception safety

const error = new Proxy(new Error('message'), {
  set: () => {
    throw new Error('example')
  },
  defineProperty: () => {
    throw new Error('example')
  },
})
setErrorProps(error, { prop: true }) // This does not throw

Related projects

• modern-errors: Handle errors in a simple, stable, consistent way
• error-custom-class: Create one error class
• error-class-utils: Utilities to properly create error classes
• error-serializer: Convert errors to/from plain objects
• normalize-exception: Normalize exceptions/errors
• is-error-instance: Check if a value is an Error instance
• 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-stack: Properly update an error's stack
• merge-error-cause: Merge an error with its cause
• 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

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

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