error-serializer

Convert errors to/from plain objects.

Features

• Ensures errors are safe to serialize with JSON
• Can be used as error.toJSON()
• Deep serialization/parsing
• Custom serialization/parsing (e.g. YAML or process.send())
• Keeps both native (TypeError, etc.) and custom error types
• Preserves errors' additional properties
• Works recursively with error.cause and AggregateError
• Normalizes invalid errors
• Safe: this never throws

Example

import { serialize, parse } from 'error-serializer'

const error = new TypeError('example')
const errorObject = serialize(error)
// Plain object: { name: 'TypeError', message: 'example', stack: '...' }

const errorString = JSON.serialize(errorObject)
const newErrorObject = JSON.parse(errorString)

const newError = parse(newErrorObject)
// Error instance: 'TypeError: example ...'

Install

npm install error-serializer

This package is an ES module and must be loaded using an import or import() statement, not require().

API

serialize(errorInstance, options?)

errorInstance any
options Options?
Return value: object

Convert an Error instance into a plain object.

Options

Object with the following optional properties.

loose

Type: boolean
Default: false

If this option is true and errorInstance is not an Error instance, it is returned as is, instead of being converted to a plain object.

console.log(serialize('example')) // { name: 'Error', message: 'example', ... }
console.log(serialize('example', { loose: true })) // 'example'

parse(errorObject, options?)

errorObject any
options Options?
Return value: Error

Convert an error plain object into an Error instance.

Options

Object with the following optional properties.

types

Type: object

Custom error types to keep when parsing.

• Each key is an errorObject.name.
• Each value is the error type to use. The constructor will be called with a single message argument. It it throws, Error will be used as the error type instead.

const errorObject = serialize(new CustomError('example'))
// `CustomError` type is kept
const error = parse(errorObject, { types: { CustomError } })
// Map `CustomError` to another type
const otherError = parse(errorObject, { types: { CustomError: TypeError } })

loose

Type: boolean
Default: false

If this option is true and errorObject is not an error plain object, it is returned as is, instead of being converted to an Error instance.

console.log(parse('example')) // Error: example
console.log(parse('example', { loose: true })) // 'example'

Usage

JSON safety

Error plain objects are always safe to serialize with JSON.

const error = new Error('example')
error.cycle = error

// Cycles make `JSON.serialize()` throw, so they are removed
console.log(serialize(error).cycle) // {}

error.toJSON()

serialize() can be used as error.toJSON().

class CustomError extends Error {
  /* constructor(...) { ... } */

  toJSON() {
    return serialize(this)
  }
}
const error = new CustomError('example')

console.log(error.toJSON())
// { name: 'CustomError', message: 'example', stack: '...' }
console.log(JSON.stringify(error))
// '{"name":"CustomError","message":"example","stack":"..."}'

Deep serialization/parsing

Objects and arrays containing errors can be deeply serialized/parsed using the loose option combined with JSON.stringify()'s replacer and JSON.parse()'s reviver.

const deepObject = [{}, { error: new Error('example') }]
const jsonString = JSON.stringify(deepObject, (key, value) =>
  serialize(value, { loose: true }),
)
const newDeepObject = JSON.parse(jsonString, (key, value) =>
  parse(value, { loose: true }),
)
console.log(newDeepObject[1].error) // Error: example

Custom serialization/parsing

Errors are converted to/from plain objects, not strings. This allows any serialization/parsing logic to be performed.

import { dump, load } from 'js-yaml'

const error = new Error('example')
const errorObject = serialize(error)
const errorYamlString = dump(errorObject)
// name: Error
// message: example
// stack: Error: example ...
const newErrorObject = load(errorYamlString)
const newError = parse(newErrorObject) // Error: example

Additional error properties

const error = new TypeError('example')
error.prop = true

const errorObject = serialize(error)
console.log(errorObject.prop) // true
const newError = parse(errorObject)
console.log(newError.prop) // true

error.cause and AggregateError

const innerErrors = [new Error('one'), new Error('two')]
const cause = new Error('three')
const error = new AggregateError(innerErrors, 'four', { cause })

const errorObject = serialize(error)
// {
//   name: 'AggregateError',
//   message: 'four',
//   stack: '...',
//   cause: { name: 'Error', message: 'three', stack: '...' },
//   errors: [{ name: 'Error', message: 'one', stack: '...' }, ...],
// }
const newError = parse(errorObject)
// AggregateError: four
//   [cause]: Error: three
//   [errors]: [Error: one, Error: two]

Error normalization

Invalid error instances or objects are normalized.

// Normalizes invalid error: not an `Error` instance
console.log(serialize('example')) // { name: 'Error', message: 'example', ... }

// Normalizes `error.name`: not a string
console.log(parse({ name: false, message: 'example' })) // Error: example

Related projects

• modern-errors: Handle errors like it's 2022 🔮
• create-error-types: Create multiple error types
• error-type: Create one error type
• normalize-exception: Normalize exceptions/errors
• merge-error-cause: Merge an error with its cause
• error-cause-polyfill: Polyfill error.cause
• handle-cli-error: 💣 Error handler for CLI applications 💥
• safe-json-value: ⛑️ JSON serialization should never fail
• log-process-errors: Show some ❤ to Node.js process errors

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!

Changelog

1.4.0

Features

• Improve error handling