Convert errors to/from plain objects
npm install error-serializer






Convert errors to/from plain objects.
- Ensures errors are safe to serialize with JSON
- Can be used as error.toJSON()
- Deep serialization/parsing, including
transforming
- Custom serialization/parsing (e.g. YAML or
process.send())
- Keeps both native (TypeError, etc.) and custom error classes
- Preserves errors' additional properties
- Can keep constructor's arguments
- Works recursively with
error.cause
and
AggregateError
- Normalizes invalid errors
- Safe: this never throws
``js
import { parse, serialize } from 'error-serializer'
const error = new TypeError('example')
const errorObject = serialize(error)
// Plain object: { name: 'TypeError', message: 'example', stack: '...' }
const errorString = JSON.stringify(errorObject)
const newErrorObject = JSON.parse(errorString)
const newError = parse(newErrorObject)
// Error instance: 'TypeError: example ...'
`
`bash`
npm install error-serializer
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.
errorInstance any\options Options?\ErrorObject
_Return value_:
Convert an Error instance into a plain object.
Object with the following optional properties.
#### shallow
_Type_: boolean\false
_Default_:
Unless this option is true, nested errors are also serialized. They can be
inside other errors, plain objects or arrays.
`js`
const error = new Error('example')
error.inner = new Error('inner')
serialize(error).inner // { name: 'Error', message: 'inner', ... }
serialize(error, { shallow: true }).inner // Error: inner ...
#### loose
_Type_: boolean\false
_Default_:
By default, when the argument is not an Error instance, it is converted totrue
one. If this option is , it is kept as is instead.
`js`
serialize('example') // { name: 'Error', message: 'example', ... }
serialize('example', { loose: true }) // 'example'
#### include
_Type_: string[]
Only pick specific properties.
`js`
serialize(error, { include: ['message'] }) // { message: 'example' }
#### exclude
_Type_: string[]
Omit specific properties.
`js`
serialize(error, { exclude: ['stack'] }) // { name: 'Error', message: 'example' }
#### transformObject(errorObject, errorInstance)
_Type_: (errorObject, errorInstance) => void
Transform each error plain object.
errorObject is the error after serialization. It must be directly mutated.
errorInstance is the error before serialization.
errorObject any\options Options?\Error
_Return value_:
Convert an error plain object into an Error instance.
Object with the following optional properties.
#### classes
_Type_: object
Custom error classes to keep when parsing.
- Each key is an errorObject.name
- Each value is the error class to use
`jsCustomError
const errorObject = serialize(new CustomError('example'))
// class is keptCustomError
const error = parse(errorObject, { classes: { CustomError } })
// Map to another class`
const otherError = parse(errorObject, { classes: { CustomError: TypeError } })
#### shallow
_Type_: boolean\false
_Default_:
Unless this option is true, nested error plain objects are also parsed. They
can be inside other errors, plain objects or arrays.
`js
const error = new Error('example')
error.inner = new Error('inner')
const errorObject = serialize(error)
parse(errorObject).inner // Error: inner ...
parse(errorObject, { shallow: true }).inner // { name: 'Error', message: ... }
`
#### loose
_Type_: boolean\false
_Default_:
By default, when the argument is not an error plain object, it is converted to
one. If this option is true, it is kept as is instead.
`js`
parse('example') // Error: example
parse('example', { loose: true }) // 'example'
#### transformArgs(constructorArgs, errorObject, ErrorClass)
_Type_: (constructorArgs, errorObject, ErrorClass) => void
Transform the arguments passed to each new Error().
constructorArgs is the array of arguments. Usually, constructorArgs[0] isconstructorArgs[1]
the
error message
and is theconstructorArgs
constructor options object. must be directly mutated.
errorObject is the error before parsing. ErrorClass is its
class.
#### transformInstance(errorInstance, errorObject)
_Type_: (errorInstance, errorObject) => void
Transform each Error instance.
errorInstance is the error after parsing. It must be directly mutated.
errorObject is the error before parsing.
Error plain objects are always
safe to serialize with JSON.
`js
const error = new Error('example')
error.cycle = error
// Cycles make JSON.stringify() throw, so they are removed`
serialize(error).cycle // undefined
serialize() can be used as
error.toJSON().
`js
class CustomError extends Error {
/ constructor(...) { ... } /
toJSON() {
return serialize(this)
}
}
const error = new CustomError('example')
error.toJSON()
// { name: 'CustomError', message: 'example', stack: '...' }
JSON.stringify(error)
// '{"name":"CustomError","message":"example","stack":"..."}'
`
Errors are converted to/from plain objects, not strings. This allows any
serialization/parsing logic to be performed.
`js
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
`
`js
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
`
`js
const error = new Error('example')
error.prop = true
const errorObject = serialize(error, { include: ['name', 'message', 'stack'] })
console.log(errorObject.prop) // undefined
console.log(errorObject) // { name: 'Error', message: 'example', stack: '...' }
`
`js
const error = new Error('example')
const errorObject = serialize(error, { exclude: ['stack'] })
console.log(errorObject.stack) // undefined
console.log(errorObject) // { name: 'Error', message: 'example' }
`
The loose option can be used to deeply serialize/parse objects and
arrays.
`js
const error = new Error('example')
const deepArray = serialize([{}, { error }], { loose: true })
const jsonString = JSON.stringify(deepArray)
const newDeepArray = JSON.parse(jsonString)
const newError = parse(newDeepArray, { loose: true })[1].error // Error: example
`
`js
const errors = [new Error('test secret')]
errors[0].date = new Date()
const errorObjects = serialize(errors, {
loose: true,
// Serialize Date instances as strings
transformObject: (errorObject) => {
errorObject.date = errorObject.date.toString()
},
})
console.log(errorObjects[0].date) // Date string
const newErrors = parse(errorObjects, {
loose: true,
// Transform error message
transformArgs: (constructorArgs) => {
constructorArgs[0] = constructorArgs[0].replace('secret', '*')
},
// Parse date strings as Date instancesDate
transformInstance: (error) => {
error.date = new Date(error.date)
},
})
console.log(newErrors[0].message) // 'test *'
console.log(newErrors[0].date) // instance`
and AggregateError`js
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]
`
By default, when an error with custom classes is parsed, its
constructor is not called. In most cases, this is not a problem since any
property previously set by that constructor is still preserved, providing it is
serializable and enumerable.
However, the error.constructorArgs property can be set to call the constructorError
with those arguments. It it throws, will be used as a fallback error
class.
`js${prefix} - ${message}
class CustomError extends Error {
constructor(prefix, message) {
super()
this.constructorArgs = [prefix, message]
}
}
CustomError.prototype.name = 'CustomError'
const error = new CustomError('Prefix', 'example')
const errorObject = serialize(error)
// This calls new CustomError('Prefix', 'example')`
const newError = parse(errorObject, { classes: { CustomError } })
- modern-errors: Handle errors in
a simple, stable, consistent way
- modern-errors-serialize:
Serialize/parse errors
- error-custom-class: Create
one error class
- error-class-utils: Utilities
to properly create error classes
- normalize-exception:
Normalize exceptions/errors
- is-error-instance: Check if
a value is an Error instancemerge-error-cause
- : Merge ancause
error with its set-error-class
- : Properlyset-error-message
update an error's class
- : Properlywrap-error-message
update an error's message
- :set-error-props
Properly wrap an error's message
- : Properlyset-error-stack
update an error's properties
- : Properlyerror-cause-polyfill
update an error's stack
- :error.cause
Polyfill handle-cli-error
- : 💣 Errorbeautiful-error
handler for CLI applications 💥
- : Prettifysafe-json-value
error messages and stacks
- : ⛑️ JSONlog-process-errors
serialization should never fail
- : Showerror-http-response
some ❤ to Node.js process errors
- :winston-error-format
Create HTTP error responses
- : Log
errors with Winston
For any question, _don't hesitate_ to submit an issue on GitHub.
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ehmicky 💻 🎨 🤔 📖 | Pedro Augusto de Paula Barbosa 🐛 📖 | JasonKleban 💻 🐛 |