@hublo/serialize-error

serialize-error

Serialize/deserialize an error into a plain object

Useful if you for example need to JSON.stringify() or process.send() the error.

Install

npm install serialize-error

Usage

import {serializeError, deserializeError} from 'serialize-error';

const error = new Error('🦄');

console.log(error);
//=> [Error: 🦄]

const serialized = serializeError(error);

console.log(serialized);
//=> {name: 'Error', message: '🦄', stack: 'Error: 🦄\n    at Object.<anonymous> …'}

const deserialized = deserializeError(serialized);

console.log(deserialized);
//=> [Error: 🦄]

Error constructors

When a serialized error with a known name is encountered, it will be deserialized using the corresponding error constructor, while unknown error names will be deserialized as regular errors:

import {deserializeError} from 'serialize-error';

const known = deserializeError({
	name: 'TypeError',
	message: '🦄'
});

console.log(known);
//=> [TypeError: 🦄] <-- Still a TypeError

const unknown = deserializeError({
	name: 'TooManyCooksError',
	message: '🦄'
});

console.log(unknown);
//=> [Error: 🦄] <-- Just a regular Error

The list of known errors can be extended globally. This also works if serialize-error is a sub-dependency that's not used directly.

import {errorConstructors} from 'serialize-error';
import {MyCustomError} from './errors.js'

errorConstructors.set('MyCustomError', MyCustomError)

Warning: Only simple and standard error constructors are supported, like new MyCustomError(message). If your error constructor requires a second parameter or does not accept a string as first parameter, adding it to this map will break the deserialization.

API

serializeError(value, options?)

Serialize an Error object into a plain object.

• Non-error values are passed through.
• Custom properties are preserved.
• Non-enumerable properties are kept non-enumerable (name, message, stack).
• Enumerable properties are kept enumerable (all properties besides the non-enumerable ones).
• Buffer properties are replaced with [object Buffer].
• Circular references are handled.
• If the input object has a .toJSON() method, then it's called instead of serializing the object's properties.
• It's up to .toJSON() implementation to handle circular references and enumerability of the properties.

value

Type: Error | unknown

toJSON implementation examples

import {serializeError} from 'serialize-error';

class ErrorWithDate extends Error {
	constructor() {
		super();
		this.date = new Date();
	}
}

const error = new ErrorWithDate();

serializeError(error);
// => {date: '1970-01-01T00:00:00.000Z', name, message, stack}

import {serializeError} from 'serialize-error';

const error = new Error('Unicorn');

error.horn = {
	toJSON() {
		return 'x';
	}
};

serializeError(error);
// => {horn: 'x', name, message, stack}

deserializeError(value, options?)

Deserialize a plain object or any value into an Error object.

• Error objects are passed through.
• Objects that have at least a message property are interpreted as errors.
• All other values are wrapped in a NonError error.
• Custom properties are preserved.
• Non-enumerable properties are kept non-enumerable (name, message, stack, cause).
• Enumerable properties are kept enumerable (all properties besides the non-enumerable ones).
• Circular references are handled.
• Native error constructors are preserved (TypeError, DOMException, etc) and more can be added.

value

Type: {message: string} | unknown

options

Type: object

maxDepth

Type: number
Default: Number.POSITIVE_INFINITY

The maximum depth of properties to preserve when serializing/deserializing.

import {serializeError} from 'serialize-error';

const error = new Error('🦄');
error.one = {two: {three: {}}};

console.log(serializeError(error, {maxDepth: 1}));
//=> {name: 'Error', message: '🦄', one: {}}

console.log(serializeError(error, {maxDepth: 2}));
//=> {name: 'Error', message: '🦄', one: { two: {}}}

useToJSON

Type: boolean
Default: true

Indicate whether to use a .toJSON() method if encountered in the object. This is useful when a custom error implements its own serialization logic via .toJSON() but you prefer to not use it.

isErrorLike(value)

Predicate to determine whether a value looks like an error, even if it's not an instance of Error. It must have at least the name, message, and stack properties.

import {isErrorLike} from 'serialize-error';

const error = new Error('🦄');
error.one = {two: {three: {}}};

isErrorLike({
	name: 'DOMException',
	message: 'It happened',
	stack: 'at foo (index.js:2:9)',
});
//=> true

isErrorLike(new Error('🦄'));
//=> true

isErrorLike(serializeError(new Error('🦄'));
//=> true

isErrorLike({
	name: 'Bluberricious pancakes',
	stack: 12,
	ingredients: 'Blueberry',
});
//=> false