Node.js module that lets you define and use errors consistently across your APIs and apps. Simple. HTTP friendly.

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Node.js module that lets you define and use errors consistently across your APIs and apps. Simple. HTTP friendly.

Example usage

var assert = require('assert');
var SimpleError = require('.');

var MyError = SimpleError.define('MyError');
var myError = new MyError('boom');

assert.ok(myerror instanceof MyError); // true
assert.ok(myerror instanceof Error); // true
assert.equal(myError.message, 'boom'); // true

var ApiError = SimpleError.define('ApiError', {
  code: 100,
  statusCode: 500,
  methods: {
    badCall: function () {
      return 'Bad call: ' + this.message;

var err = new ApiError('NO!');

assert.equal(err.type, 'ApiError'); // true
assert.equal(, 'ApiError'); // true
assert.equal(err.code, 100);        // true
assert.equal(err.statusCode, 500);  // true

// {"success":false,"message":"NO!","statusCode":400,"code":101}

console.log(err.badCall()); // Bad call: NO!

assert.ok(err instanceof Error); // true
assert.ok(err instanceof ApiError); // true

var util = require('util');

// Warning! Does not work with node.js util.isError method
util.isError(err); // false

// Sub errors
var BadRequestError = ApiError.define('BadRequestError', {
  code: 102,
  statusCode: 400,
  message: 'Bad request',
  methods: {
    hello: function () {
      return 'well, hello!';

var bad = new BadRequestError();

assert.ok(bad instanceof Error);           // true
assert.ok(bad instanceof ApiError);        // true
assert.ok(bad instanceof BadRequestError); // true

bad.hello(); // well, hello!

// inherited from ApiError
bad.badCall(); // Bad call: Bad request

// Wrapping unknown exceptions
var e = new Error('oops');
var wrappedError = BadRequestError.wrap(e);

assert.ok(wrappedError instanceof ApiError);        // true
assert.ok(wrappedError instanceof BadRequestError); // true
assert.equal(wrappedError.inner, e);                // true

// {"success":false,"message":"oops","statusCode":400,"code":102}

// Custom error consctructor if needed
var BasicError = SimpleError.define('BasicError', {
   code: 1234,
   statusCode: 400,
   message: 'Error with custom constructor',
   ctor: function (errorCode, links) {
     this.errorCode = errorCode;
     this.links = links;

var links = ['', ''];
var err = new BasicError(101, links);

Error definition defaults and options

There are some "sensible" defaults when it comes to defining your errors.

code (any value)

Meant to be used as an internal code for other apps or APIs. Default is 0.

statusCode (integer)

HTTP error status code. Default is 500.

message (string)

Message format string. Called by node's util.format for interpolation if needed. Default is Unknown.

exclude (arraystring)

Properties to exclude when calling friendly method. For example: exclude: ['code', 'foo', 'bar', 'baz']. Properties that are always excluded are ['isError', 'type', 'name']

showStack (boolean)

When set to true stacktrace is included in toJSON call. Default is false

ctor (function)

If supplied will be used in new error construction as a constructor. See tests.

methods (dict of functions)

If supplied all the methods will be copied to prototype and thus available on all instances of that error type. See tests.

Instance methods


Returns a frendly error object with properties excluded defined in exclude option

Class methods


Takes an error and returns an new instance of error with passed in error set as .inner property and all other properties copied over to new instance.