Create HTTP errors with additional properties for any framework.

http://sw.cowtech.it/http-errors-enhanced

Just run:

npm install http-errors-enhanced --save

You can create an error by using the generic base class.

import { HttpError } from 'http-errors-enhanced'

// Any of the following will return the same error
const error1 = new HttpError(404, 'Page not found.', { key1: 'prop1' })
const error2 = new HttpError(404, { key1: 'prop1', message: 'Page not found.' })
const error3 = new HttpError('NotFound', 'Page not found.')
const error4 = new HttpError('NotFound', { key1: 'prop1', message: 'Page not found.' })

Or you can import a specific error class and instantiate that, to have some status and messages set up for you automatically.

import { NotFoundError } from 'http-errors-enhanced'

// Any of the following will return the same error
const error1 = new NotFoundError('Page not found.', { key1: 'prop1' })
const error2 = new NotFoundError({ key1: 'prop1', message: 'Page not found.' })

Or, if you don't want to use the new operator, you can use the createError function:

import { createError } from 'http-errors-enhanced'

// Any of the following will return the same error
const error1 = createError(404, 'Page not found.', { key1: 'prop1' })
const error2 = createError(404, { key1: 'prop1', message: 'Page not found.' })
const error3 = createError('NotFound', 'Page not found.')
const error4 = createError('NotFound', { key1: 'prop1', message: 'Page not found.' })

The main error class.

The constructor signature is the following:

constructor(status, message, properties)

Where:

• status: A HTTP status code as number or a identifier (like: NotFound). If the identifier is not valid or the number outside the validity range (400 <= status <= 599), it defaults to 500.
• message: The error message. This is optional.
• properties: A list of additional properties to attach to the error. With the exception of code, message, stack, expose and headers, all properties that already exist in the object are ignored. This is optional.

The returned instance is a descendant class of Error with the following base properties, plus all the other properties specified in the constructor:

• status: The HTTP status as number.
• statusCode: It always mirrors status. It exists for compatibility reasons.
• statusClass: The HTTP status class, which is its first digit multiplied by 100. For instance, the status class of 404 is 400.
• code: A string identifier for the error. If not ovewritten using properties, it always starts with HTTP_ERROR_ (this prefix is also exported as HttpError.standardErrorPrefix). If the status code is know, it will be a string representation of it, like HTTP_ERROR_NOT_FOUND, otherwise it will contain the status number, like HTTP_ERROR_570.
• error: The HTTP status code description, if found. Example: Not Found.
• errorPhrase: The HTTP status code as phrase, if found. Example: Not found..
• expose: A boolean to notify frameworks if errors internals (like message and stack) should be sent to client. Unless overwritten, it is set to true for errors whose statusClass is 400.
• headers: An object of HTTP headers to send to the client.
• isClientError: This is set to true if the HTTP status class is 400.
• isServerError: This is set to true if the HTTP status class is 500.

Each instance has a serialize(extended, omitStack) function.

If called without argument, it will return a object with the properties statusCode, error and message copied from the instance.

If called with extended set to true, it will call serializeError (see below) on the instance.

For each known HTTP error, taken from Node.js http.STATUS_CODES, there is an exported named class.

For instance, for the HTTP error 404, there is the NotFoundError which inherits from HttpError.

The constructor of a named class is the following:

constructor([message], [properties])

The function can be used to create an HttpError without using the new operator.

It accepts the same arguments of the HttpError constructor.

The function can be used to check if an value is a HttpError or it has compatible properties. It follows the same semantic of the hononym function of http-errors.

The function returns true if the value is an instance of HttpError or if the value is an object with a status property which is a number (and it is mirrored by the statusCode property) and a expose property which is a boolean.

Copies all enumerable properties from source to target, skipping the ones which are already defined.

The function extracts the message, code (or name if no code is present) and stack properties from an object (typically a descendant of Error).

The extract properties are formatted and returned in a plain object containing message (string) and stack (array of strings) properties.

The object also contains all the other properties of the original object.

If omitStack is true, the stack property is omitted.

The package exports several utility constants to make HTTP status handling easier

A map of statuses identifiers indexed by HTTP status code and its reverse. This also exports HTTP classes 100, 200 and 300.

console.log(identifierByCodes[404])
// => NotFound

console.log(codesByIdentifier['NotFound'])
// => 404

A map of statuses descriptions and phrases indexed by HTTP status code. This also exports HTTP classes 100, 200 and 300.

console.log(messagesByCodes[404])
// => Not Found

console.log(phrasesByCodes[404])
// => Not found.

For each HTTP status there is a upper snake case constant exported.

console.log(CREATED)
// => 201

console.log(NOT_FOUND)
// => 404

The package defines a schema for commonly used error codes, in order to easily include them in JSON Schema and OpenAPI based validation frameworks.

console.log(JSON.stringify(notFoundErrorSchema))
/*
=> {
  "type": "object",
  "$id": "errors/404",
  "description": "Error returned when the requested resource is not found.",
  "properties": {
    "statusCode": {
      "type": "number",
      "description": "The error code",
      "enum": [
        404
      ],
      "example": 404
    },
    "error": {
      "type": "string",
      "description": "The error title",
      "enum": [
        "NotFound"
      ],
      "example": "NotFound"
    },
    "message": {
      "type": "string",
      "description": "The error message",
      "pattern": ".+",
      "example": "NotFound."
    }
  },
  "required": [
    "statusCode",
    "error",
    "message"
  ],
  additionalProperties: false
}
*/

This package only supports to be directly imported in a ESM context.

For informations on how to use it in a CommonJS context, please check this page.

This project has been heavily inspired by http-errors, of which is a indipendent and unrelated project.

• Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet.
• Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it.
• Fork the project.
• Start a feature/bugfix branch.
• Commit and push until you are happy with your contribution.
• Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.

Copyright (C) 2020 and above Shogun (shogun@cowtech.it).

Licensed under the ISC license, which can be found at https://choosealicense.com/licenses/isc.