Building for clients with Node.js @PabloSerbo Paul Serby 

Overview About us Why node.js Our approach - code examples Client projects Pain points - code examples Did we make the right decision? 

@clock www.clock.co.uk 

Frontend / Design / UX Backend / Devops Clock Team 

1997 

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Paul Serby http://github.com/serby @PabloSerbo 10 years at Clock CTO since 2005 Computer Science Degree 

Why node.js 

Fatigue 

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Frontend / Design / UX Backend / Devops Clock Team 

Frontend / Design / UX Backend / Devops PHP Skills 

Frontend / Design / UX Backend / Devops JavaScript Skills 

Community 

Our approach 

jade hook.io connect express stylus socket.io mongodb mocha should.js winston async underscore jshint 

Crockford on JavaScript - Act III: Function the Ultimate - http://bit.ly/xooF1h Module Pattern Pseudo-classical inheritance - “This was the inheritance scheme that was designed for the language, and I really don't care for it at all. I don't think it looks very good.” 

var EventEmitter = require('events').EventEmitter; exports.createKitten = function() { var dead = false , energy = 0 , kitten = new EventEmitter(); function eat() { deadCheck(); energy += 10; } function run() { deadCheck(); if (energy > 1) { energy -= 1; } else { die(); } } function die() { kitten.emit('died', self); deadCheck(); dead = true; } function deadCheck() { if (dead) { throw new Error('You are dead'); } } kitten.eat = eat; kitten.run = run; return self; }; var util = require('util') , events = require('events'); function Kitten() { events.EventEmitter.call(this); } function deadCheck(kitten) { if (kitten.dead) { throw new Error('You are dead'); } } util.inherits(Kitten, events.EventEmitter); Kitten.prototype.energy = 0; Kitten.prototype.dead = 0; Kitten.prototype.eat =function() { deadCheck(this); this.energy += 10; }; Kitten.prototype.run =function() { deadCheck(this); if (this.energy > 1) { this.energy -= 1; } else { this.die(); } }; Kitten.prototype.die = function () { this.emit('died', this); deadCheck(this); this.dead = true; }; exports.Kitten = Kitten; 

Inversion of Control 

var serviceLocator = require('service-locator').createServiceLocator() , foo = 'bar'; serviceLocator.register('foobar', foo); console.log(serviceLocator.foobar); // bar serviceLocator.register('logger', console); serviceLocator.logger.log('Hello world'); // Hello world http://github.com/serby/service-locator Inversion of Control 

Most modules should have exactly 1 export. Module systems should be designed around that use case first, not for dozens of exports. substack Separation of concerns if your module exposes more than one function, you might be doing it wrong :) mikeal 

OBJECT ORIENTED MASTURBATION Playing with yourself 

Moduleitus exports.createMathLib = function () { var answer = NaN; return { sum: function (x, y) { answer = x + y; }, get answer() { return answer; } }; }; var math = require('math-lib').createMathLib() , printer = require('printer').createPrinter(); math.sum(1, 1); printer.setPrefix('The answer is: '); printer.out(math.answer); exports.createPrinter = function() { var prefix = ''; return { setPrefix: function(value) { prefix = value; }, out: function(value) { console.log(prefix + value); } }; }; http://robert.accettura.com/blog/2008/12/16/object-oriented-masturbation/ npm install math-lib npm install printer 

function sum(x, y) { return x + y; } console.log('The answer is: ' + sum(1, 1)); Sanity 

Client Projects 

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Usage Stats 104,922 Registrations Ran for 1 month Read: 950 per second at peak 150 reg per second at 

Commercial Stats 40% Profit Sun Perks Phase 1 12 Month Average 32% Profit 

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Usage Stats 154,359 Registrations Ran for 3 months Benchmarked at 250 per second 

Commercial Stats 31% Profit Sun Perks Phase 2 12 Month Average 32% Profit 

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Commercial Stats 40% Profit Eat Out Phase 1 12 Month Average 32% Profit 

Commercial Stats 55% Profit Eat Out Phase 2 12 Month Average 32% Profit 

Commercial Stats 40% Profit Average over both project 

Pain Points 

Async 

Async 

Sync var userModel = require('../lib/userModelSync').createUserModel(); module.exports.findMe = function(user){ return userModel.findByEmail(user.email) || userModel.findByName(user.name) || userModel.findByGithub(user.github)) || null; }; 

var userModel = require('../lib/userModel').createUserModel(); module.exports.findMe = function(user, callback) { userModel.findByEmail(user.email, function(error, foundUser) { if (error) { return callback(error); } if (foundUser === null) { userModel.findByName(user.name, function(error, foundUser) { if (error) { return callback(error); } if (foundUser === null) { userModel.findByGithub(user.github, function(error, foundUser) { if (error) { callback(error); } if (foundUser === null) { callback(null, null); } else { callback(null, foundUser); } }); } else { callback(null, foundUser); } }); } else { callback(null, foundUser); } }); }; 

var userModel = require('../lib/userModel').createUserModel(); module.exports.findMe = function(user, callback) { userModel.findByEmail(user.email, function(error, foundUser) { if (error) { return callback(error); } if (foundUser === null) { userModel.findByName(user.name, function(error, foundUser) { if (error) { return callback(error); } if (foundUser === null) { userModel.findByGithub(user.github, function(error, foundUser) { if (error) { return callback(error); } if (foundUser === null) { callback(null, null); } else { callback(null, foundUser); } }); } else { callback(null, foundUser); } }); } else { callback(null, foundUser); } }); }; 

var userModel = require('../lib/userModel').createUserModel(), step = require('step'); module.exports.findMe = function(user, callback){ step( function() { userModel.findByName(user.name, this); }, function(error, result) { if (error || result) { this(error, result); } else { userModel.findByEmail(user.email, this); } }, function(error, result) { if (error || result) { this(error, result); } else { userModel.findByGithub(user.github, this); } }, function(error, result) { callback(error, result); } ); }; Step https://github.com/creationix/step 

var userModel = require('../lib/userModel').createUserModel(), async = require('async'); module.exports.findMe = function(user, callback){ var foundUser, foundError; async.detectSeries( [ async.apply(userModel.findByEmail, user.email), async.apply(userModel.findByName, user.name), async.apply(userModel.findByGithub, user.github) ], function (fn, cb) { fn(function(error, user) { foundUser = user; foundError = error; cb(foundError || user); }); }, function(result) { callback(foundError, foundUser); } ); }; async https://github.com/caolan/async 

var userModel = require('../lib/userModel').createUserModel(); module.exports.findMe = function(user, callback){ var fns = [ userModel.findByEmail.bind(this, user.email), userModel.findByName.bind(this, user.name), userModel.findByGithub.bind(this, user.github), function() { return callback(undefined, null); } ]; function detect(error, user) { if (error || user) { return callback(error, user); } fns.shift()(detect); } detect(); }; none 

var userModel = require('../lib/userModel').createUserModel(), chain = require('jangle').chain; module.exports.findMe = function(user, callback){ chain() .seq(userModel.findByName, user.name) .seq(userModel.findByEmail, user.email) .seq(userModel.findByGithub, user.github) .detect(function(error, returnedUser) { return returnedUser; }) .run(callback); }; jangle https://github.com/serby/flow-control-examples 

NPM Modules http://www.mikealrogers.com/posts/nodemodules-in-git.html 

NPM Modules http://www.mikealrogers.com/posts/nodemodules-in-git.html GIT 

Did we make the right decision? 

Questions?