extend-error's Introduction

extend-error

Ever tried to create custom error types in Node.js and wished it should be this simple?

var MyError = Error.extend('MyError');

throw MyError('wow')

installation

npm install extend-error

and in your app.js, just require('extend-error'). It will provide you an extend() method for the Error type.

syntax

extend() takes two arguments : subTypeName & errorCode [optional]
it returns the newly created error type

more examples for a web app

something useful

var AppError = Error.extend('AppError', 500);
var ClientError = Error.extend('ClientError', 400);

extend ClientError further for specific http types

var HttpNotFound = ClientError.extend('HttpNotFoundError', 404);
var HttpUnauthorized = ClientError.extend('HttpUnauthorized', 401);

throwing errors

throw new AppError('unable to connect db due to error: ' + err);

throw new ClientError({'message':'required field missing', field: 'email'})

throw new HttpNotFound('no post found with id: ' + id);

throw new HttpNotFound({'message': 'no such post', 'id': id});

don't worry when you forget 'new'

throw ClientError('bad request');

instanceof

throw an error in controller

var err = HttpNotFound('user profile not found');

throw err; 
(or)
callback(err)

handle it easily in global error handler (in case of express.js error middleware)

if (err instanceof ClientError) {
	//send out the actual message
	res.send(err.code, err.message);
} else {
	//send out a generic message
	res.send(500, 'oops! something went wrong');
	log.error(err);
}

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extend-error's Issues

Consider using own method

Would you consider using a custom method for extending vs augmenting the native Error Object with the extent() method?

i.e.

var extendError = require('extend-error');

var CustomError = extendError('CustomError');

Please bump version and publish to NPM

There are merged changes that are not in NPM yet, such as the error name being displayed wrong due to using string replace. Please bump version in NPM so we can use the latest fixes. Thanks!

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