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standard-http-error

2.0.1 • Public • Published

StandardHttpError.js

NPM version Build status

StandardHttpError.js is a very simple but useful error class for JavaScript and Node.js that represents HTTP errors. You can then detect it with instanceof in error handling middleware and act accordingly. Also works in the browser through Browserify.

You can use StandardHttpError.js with any error code you like, standardized or not. They don't have to exist beforehand, so if you're living on the cutting edge, feel free to use new HttpError(451, "Unavailable For Legal Reasons").

Installing

npm install standard-http-error

StandardHttpError.js follows semantic versioning, so feel free to depend on its major version with something like >= 1.0.0 < 2 (a.k.a ^1.0.0).

Using

var HttpError = require("standard-http-error")
throw new HttpError(404)

Your error handler will then receive an instance of HttpError along with the following enumerable properties:

Property Value
name "HttpError"
code 404
message "Not Found"

As always for errors, the non-enumerable stack property is there as well.

For compatibility with Express or Koa's default request handler (the one that prints your errors out if you don't handle them), StandardHttpError.js also sets status, statusCode and statusMessage to be aliases of code and message. They're non-enumerable to not pollute serialization.

Creating a new instance by error name

StandardHttpError.js also supports passing a constant name instead of the error code.

new HttpError("NOT_FOUND")
new HttpError("FORBIDDEN")

See below for a list of error code names.

Setting a custom message

new HttpError(412, "Bad CSRF Token")

The default "Precondition Failed" message that the error code 412 would've resulted in will then be replaced by "Bad CSRF Token".

Note that status messages were always meant to be human readable, so it's perfect fine and even preferable to provide clarification in the status message. Try to stick to the capitalized form, though, as that will match the default HTTP status message style.

Setting custom properties

You can pass custom properties to be attached to the error instance as an object:

new HttpError(404, {url: req.url})
new HttpError(412, "Bad CSRF Token", {session: req.session})

You can access the given session property then as err.session.

Subclassing StandardHttpError

If you wish to add your own functionality to StandardHttpError, subclass it:

var HttpError = require("standard-http-error")
 
function RemoteError(res) {
  HttpError.call(this, res.statusCode, res.statusMessage)
}
 
RemoteError.prototype = Object.create(HttpError.prototype, {
  constructor: {value: RemoteError, configurable: true, writeable: true}
})

The StandardError.js library that StandardHttpError.js uses makes sure the name and stack properties of your new error class are set properly.

If you don't want your new error class to directly inherit from StandardHttpError, feel free to leave the RemoteError.prototype line out. Everything will work as before except your RemoteError will no longer be an instanceof StandardHttpError.js. You might want to manually grab the HttpError.prototype.toString function then though, as that's useful for nice String(err) output.

Switching based on error codes

switch (err.code) {
  case HttpError.UNAUTHORIZED: return void res.redirect("/signin")
  case HttpError.NOT_FOUND: return void res.render("404")
  case 451: return void res.redirect("/legal")
  default: return void res.render("500")
}

Using with Express

StandardHttpError.js comes very handy when used with Connect/Express's error handling functionality:

var HttpError = require("standard-http-error")
var app = require("express")()
 
app.get("/account", function(req, res, next) {
  if (req.account == null) throw new HttpError(401)
  if (req.account.budget == 0) throw new HttpError(402)
  // ...
})
 
app.use(function(err, req, res, next) {
  if (!(err instanceof HttpError)) return void next(err)
 
  res.statusCode = err.code
  res.statusMessage = err.message
  res.render("error", {title: err.message})
})

Error Codes

StandardHttpError.js comes with a list of status message constants that you can use for comparison and in switch statements.

HttpError.NOT_FOUND // => 404

When running on Node.js, cached status codes and their names get merged with new codes from Http.STATUS_CODES. Existing status codes will not be changed without bumping StandardHttpError.js's major version number. That ensures consistent constants in Node and in the browser.

Code Name
100 CONTINUE
101 SWITCHING_PROTOCOLS
102 PROCESSING
200 OK
201 CREATED
202 ACCEPTED
203 NON_AUTHORITATIVE_INFORMATION
204 NO_CONTENT
205 RESET_CONTENT
206 PARTIAL_CONTENT
207 MULTI_STATUS
208 ALREADY_REPORTED
226 IM_USED
300 MULTIPLE_CHOICES
301 MOVED_PERMANENTLY
302 FOUND
303 SEE_OTHER
304 NOT_MODIFIED
305 USE_PROXY
307 TEMPORARY_REDIRECT
308 PERMANENT_REDIRECT
400 BAD_REQUEST
401 UNAUTHORIZED
402 PAYMENT_REQUIRED
403 FORBIDDEN
404 NOT_FOUND
405 METHOD_NOT_ALLOWED
406 NOT_ACCEPTABLE
407 PROXY_AUTHENTICATION_REQUIRED
408 REQUEST_TIMEOUT
409 CONFLICT
410 GONE
411 LENGTH_REQUIRED
412 PRECONDITION_FAILED
413 PAYLOAD_TOO_LARGE
414 URI_TOO_LONG
415 UNSUPPORTED_MEDIA_TYPE
416 RANGE_NOT_SATISFIABLE
417 EXPECTATION_FAILED
418 IM_A_TEAPOT
421 MISDIRECTED_REQUEST
422 UNPROCESSABLE_ENTITY
423 LOCKED
424 FAILED_DEPENDENCY
425 UNORDERED_COLLECTION
426 UPGRADE_REQUIRED
428 PRECONDITION_REQUIRED
429 TOO_MANY_REQUESTS
431 REQUEST_HEADER_FIELDS_TOO_LARGE
500 INTERNAL_SERVER_ERROR
501 NOT_IMPLEMENTED
502 BAD_GATEWAY
503 SERVICE_UNAVAILABLE
504 GATEWAY_TIMEOUT
505 HTTP_VERSION_NOT_SUPPORTED
506 VARIANT_ALSO_NEGOTIATES
507 INSUFFICIENT_STORAGE
508 LOOP_DETECTED
509 BANDWIDTH_LIMIT_EXCEEDED
510 NOT_EXTENDED
511 NETWORK_AUTHENTICATION_REQUIRED

License

StandardHttpError.js is released under a Lesser GNU Affero General Public License, which in summary means:

  • You can use this program for no cost.
  • You can use this program for both personal and commercial reasons.
  • You do not have to share your own program's code which uses this program.
  • You have to share modifications (e.g. bug-fixes) you've made to this program.

For more convoluted language, see the LICENSE file.

About

Andri Möll typed this and the code.
Monday Calendar supported the engineering work.

If you find StandardHttpError.js needs improving, please don't hesitate to type to me now at andri@dot.ee or create an issue online.

install

npm i standard-http-error

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12,075

version

2.0.1

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homepage

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repository

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