serialize-error

What is serialize-error?

The serialize-error npm package is used to serialize error objects into plain objects, retaining as much information as possible. It can be useful for logging errors or sending them over the network, as standard Error objects may not be properly serialized by default JSON.stringify.

What are serialize-error's main functionalities?

Serialize an Error object

This feature allows you to serialize a standard Error object into a JSON-friendly format, including properties like name, message, and stack.

{"error": {"name": "Error", "message": "An error occurred!", "stack": "Error: An error occurred!\n    at Object.<anonymous> (/path/to/file.js:2:15)\n    at Module._compile (internal/modules/cjs/loader.js:1137:30)\n    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1157:10)\n    at Module.load (internal/modules/cjs/loader.js:985:32)\n    at Function.Module._load (internal/modules/cjs/loader.js:878:14)\n    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)\n    at internal/main/run_main_module.js:17:47"}}

Serialize custom error properties

This feature allows you to serialize Error objects that have custom properties beyond the standard Error properties.

{"error": {"name": "CustomError", "message": "Something custom happened!", "customProperty": "Custom value", "stack": "CustomError: Something custom happened!\n    at Object.<anonymous> (/path/to/file.js:2:15)\n    at Module._compile (internal/modules/cjs/loader.js:1137:30)\n    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1157:10)\n    at Module.load (internal/modules/cjs/loader.js:985:32)\n    at Function.Module._load (internal/modules/cjs/loader.js:878:14)\n    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)\n    at internal/main/run_main_module.js:17:47"}}

Other packages similar to serialize-error

error-to-json

This package is similar to serialize-error in that it provides a way to serialize error objects to JSON. It may differ in the specific implementation or additional options provided for serialization.

serialize-javascript

While not exclusively for error objects, serialize-javascript allows for the serialization of JavaScript expressions, including errors. It can serialize functions, regexes, and dates, in addition to errors, which may make it more versatile in some scenarios compared to serialize-error.

README

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