Custom Error Classes

• All classes inherit from the abstract class (lib/abstract-error.js) inspired by dustin senos's post.
• The abstract error class inherits from the in built error object.
• All error classes exported in lib/main.js -> index.js

App Error Classes (module.exports.general)

1. ValidationError
2. DatabaseError

Express Error Classes (module.exports.request)

1. BadRequest = Bad Request Error (400)
2. Unauthorized = Unauthorized Error (401)
3. Forbidden = Forbidden Error (403)
4. NotAcceptable Request Not Acceptable Error (406)

Sample Usage

1. General Error Classes

var main = require('./../lib/main');
var ValidationError = main.general.ValidationError;

var msg = "terrible input",
	ValError = new BadRequest(msg);

console.log('ValError', ValError);

STDOUT output:

ValError {
	name: 'Validation',
	logLevel: 'warn',
	resCode: undefined,
	message: 'not a valid date'
}

2. Request Error Classes

var BadRequestError = main.request.BadRequest;
var msg = "just an awful request",
	ReqError = new BadRequestError(msg);

console.log('ReqError', ReqError);

STDOUT output:

ReqError {
	name: 'BadRequest',
	logLevel: 'warn',
	resCode: 400,
	message: 'just an awful request'
}

In-App Usage eg in Express

// route definitions
var customErrors = require('customErrors');
var BadRequestError = customErrors.request.BadRequest;

app.get('/some/route', function(req, res, next) {
	if ('error thrown') {
		next(new BadRequestError('reason for the bad request being thrown'));
	}
});

// catchall error middleware (put at very end underneath all routes)
var	util = require('util');
var Log = require('log');
var	log = new Log();
var customErrors = require('customErrors');
var BadRequestError = customErrors.request.BadRequest;

app.use(function(err, req, res, next) {

	if (err instanceof BadRequestError && app.get('env') === 'production') {
		// use visionmedia's logger to write to main app logfile
		var logLevel = err.logLevel || 'debug';
		var logger = log[logLevel];
		var seriousErrors = ['error', 'critical', 'alert', 'emergency'];

		// log the error summary with visionmedia's logger
		logger(err.name + ': ' + err.message);

		// if it's a serious error then dump some more info for debugging purposes
		if (seriousErrors.indexOf(logLevel) !== -1) {
			console.log(err.stack);
		}

	} else {
		// if in dev then deeply inspect every error
		console.log(err.name || 'express error', util.inspect(err, true, 4, true));
	}

	res.send(err.resCode || 500, {error: err.name || "there was an error"});
});

TODO

1. add more tests
2. add visionmedia's log as dependency -> walk thru list of methods and throw error logLevel property is not a method

eg this shd throw:

errFactory('Database', 'err')

eg this is correct:

errFactory('Database', 'error')

Reference

Header status codes

log levels

Visionmedia Logging Module

0 EMERGENCY system is unusable
1 ALERT action must be taken immediately
2 CRITICAL the system is in critical condition
3 ERROR error condition
4 WARNING warning condition
5 NOTICE a normal but significant condition
6 INFO a purely informational message
7 DEBUG messages to debug an application