modern-error

A modern take on JavaScript errors

modern-error is a drop-in replacement for the native Error class, with slightly more modern features:

Create and throw errors with additional properties in one line
Instantiate errors with a string, object, or existing native error
Serialize the message property to JSON by default, without the need for a JSON replacer function or subclass
Customize which non-enumerable properties are serialized without subclassing
Easily define subclasses with default properties

Installation

npm install modern-error

Usage

// Modules
import ModernError from 'modern-error';
// CommonJS
const ModernError = require('modern-error');

Create an error with a message

throw new ModernError('An error occurred');

Create an error with a message and additional properties

throw new ModernError('An error occurred', { code: 'D12' });

Create an error with an object

throw new ModernError({
  message: 'An error occurred',
  code: 'D12',
  test: true
});

Create an error by wrapping a native Error object

const nativeError = new Error('An error occurred');
nativeError.code = 'D12';
throw new ModernError(nativeError);
// The 'message' and 'code' properties are inherited from the native error object

Subclassing

modern-error is designed to be easily extensible.

class CustomError extends ModernError {}
const error = new CustomError();
console.log(error instanceof CustomError); // true

Subclasses may also define custom properties by overriding the static ‘defaults’ getter

class ErrorWithDefaults extends ModernError() {
  static get defaults() {
    return {
      test: false,
      code: null,
      details: 'No further details'
    };
  }
}
const error = new ErrorWithDefaults('Test', { code: 'D12' });
// error's properties are:
// message: 'Test'
// test: false
// code: 'D12'
// details: 'No further details'

Subclasses may alternatively be created by invoking the static subclass function.

const HTTPError = ModernError.subclass({
  name: 'HTTPError',
  defaults: { status: 500 },
  serialize: ['message', 'stack']
});
const error = new HTTPError('Error occurred');
// error's properties are:
// message: Error occurred
// status: 500

Defaults

Defaults properties for instances of ModernError may be defined by setting the class defaults property:

ModernError.defaults = {
  status: 500,
  test: false
};

Or overriding the defaults static function of a subclass:

class ErrorWithDefaults extends ModernError() {
  static get defaults() {
    return {
      status: 500,
      test: false
    };
  }
}

Or, finally, by declaring defaults in a quick subclass:

const ErrorWithDefaults = ModernError.subclass({
  defaults: {
    status: 500,
    test: false
  }
});

Serialization

modern-error serializes its non-enumerable message property to JSON by default. You may also specify which other non-enumerable properties to serialize without subclassing by setting the class property serialize.

ModernError.serialize = ['message', 'stack'];
// From now on, all JSON representations of a ModernError will include the `stack` property

Or overriding the getter in a subclass.

class StackError extends ModernError {
  static get serialize() {
    return ['message', 'stack'];
  }
}
const error = new StackError('An error has occurred');
console.log(JSON.stringify(error));
// JSON representation will include the `stack` property

All property keys are sorted alphabetically before serialization.