Bonnes pratiques de développement avec Node js

Bonnes pratiques de
développement avec Node.js
François Zaninotto
@francoisz http://github.com/fzaninotto

Node.js ne sufﬁt pas
et vous ne pouvez pas réinventer la roue

Organisation du code
Objectif: éviter le code spaghetti
Utiliser un framework pour les applis web
visionmedia/express (ou viatropos/tower)

Eviter la course aux callbacks
caolan/async (ou kriskowal/q)

Inclure des routes et monter des sous-applications
«Fat model, Skinny controller»
Modules de service pour éviter un modèle trop fat

// main app.js
var express = require('express');
var app = module.exports = express.createServer();

app.configure(function(){
app.use(app.router);
// these middlewares are required by some of the mounted apps
app.use(express.bodyParser());
app.use(express.methodOverride());
app.use(express.cookieParser());
app.use(express.session({ secret: 'qdfegfskqdjfhskjdfh' }));
});

// Routes
app.use('/api', require('./app/api/app'));
app.use('/dashboard', require('./app/dashboard/app'));
app.get('/', function(reaq, res) {
res.redirect('/dashboard/events');
});

app.listen(3000);

// dashboard app
var express = require('express');
var app = module.exports = express.createServer();

app.configure(function(){
app.use(app.router);
app.set('views', __dirname + '/views');
app.set('view engine', 'ejs');
app.use(express.static(__dirname + '/public'));
});

// Routes
app.get('/events', function(req, res) {
res.render('events', { route: app.route });
});
app.get('/checks', function(req, res) {
res.render('checks', { route: app.route, info: req.flash('info')});
});
//...
if (!module.parent) {
app.listen(3000);
}

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Uptime</title>
<link rel="stylesheet" href="<%= route %>/stylesheets/bootstrap.css">
<link rel="stylesheet" href="<%= route %>/stylesheets/style.css">
</head>
<body>
<div class="navbar">
<div class="navbar-inner">
<div class="container">
<a class="brand" href="<%= route %>/events">Uptime</a>
<ul class="nav pull-left">
<li><a href="<%= route %>/events">Events</a></li>
<li><a href="<%= route %>/checks">Checks</a></li>
<li><a href="<%= route %>/tags">Tags</a></li>
</ul>
</div>
</div>
</div>

Standards
Felix's Node.js Style Guide
(http://nodeguide.com/style.html)

Object-Oriented Programming FTW

Domain-Driven Design!

Canaux de communication
Dans un module
Entre applications Client / Serveur
ou une application

Appels de
Notiﬁcations Events socket.io
méthodes

Echanges de Appels de XMLHTTP
API HTTP
données méthode Request

Traitements
Promise AMQP Mentir*
asynchrones

// server-side
var socketIo = require('socket.io');
var CheckEvent = require('./models/checkEvent');

var io = socketIo.listen(app);

CheckEvent.on('postInsert', function(event) {
io.sockets.emit('CheckEvent', event.toJSON());
});

// client-side
<!DOCTYPE html>
<html lang="en">
<head>
<script src="/socket.io/socket.io.js"></script>
<script>var socket = io.connect('http://'+location.hostname);</script>
</head>
<body>
<div class="navbar"><ul id="counts"></ul></div>
<script>
$(document).ready(function() {
var updateCounts = function() {
$.getJSON('/api/check/count', function(count) {
// display counts in navbar
});
};
updateCounts();
socket.on('CheckEvent', function() {
updateCounts();
$('#count').fadeOut().fadeIn().fadeOut().fadeIn();
});
});
</script>
</body>
</html>

Gestions des erreurs
try {} catch {} ne marche pas en asynchrone
function (err, results) est la signature
standard des callbacks asynchrones
"Leave early"
Utiliser les codes d’erreur HTTP pour les APIs

app.delete('/check/:id', function(req, res, next) {
Check.findOne({ _id: req.params.id }, function(err, check) {
if (err) {
return next(err);
}
if (!check) {
return next(new Error('No check with id ' + req.params.id));
}
check.remove(function(err2){
if (err2) {
req.flash('error', 'Error - Check not deleted');
res.redirect('/checks');
return;
}
req.flash('info', 'Check has been deleted');
res.redirect('/checks');
});
});
});

Tests Unitaires
Librairies (presque) standard
Assertions : visionmedia/should.js (ou node/assert)

TDD : visionmedia/mocha (ou caolan/node-unit)
BDD : visionmedia/mocha (ou mhevery/jasmine-node)

L’asynchrone se teste aussi très bien
Pas besoin de mocker quand on peut monkey-patcher

describe('Connection', function(){
var db = new Connection
, tobi = new User('tobi')
, loki = new User('loki')
, jane = new User('jane');

beforeEach(function(done){
db.clear(function(err){
if (err) return done(err);
db.save([tobi, loki, jane], done);
});
})

describe('#find()', function(){
it('respond with matching records', function(done){
db.find({ type: 'User' }, function(err, res){
if (err) return done(err);
res.should.have.length(3);
done();
})
})
})
})

var nock = require('nock');

var couchdb = nock('http://myapp.iriscouch.com')
.get('/users/1')
.reply(200, {
_id: "123ABC",
_rev: "946B7D1C",
username: 'pgte',
email: 'pedro.teixeira@gmail.com'}
);

Projet open-source
Conﬁgurable
app.configure() pas compatible avec un SCM
lorenwest/node-config (ou flatiron/nconf)

Extensible
Custom events
Plugin architecture

// in main app.js
path.exists('./plugins/index.js', function(exists) {
if (exists) {
require('./plugins').init(app, io, config);
};
});

// in plugins/index.js
exports.init = function(app, io, config) {
require('./console').init();
}

module.exports = exports = function lifecycleEventsPlugin(schema) {
schema.pre('save', function (next) {
var model = this.model(this.constructor.modelName);
model.emit('preSave', this);
this.isNew ? model.emit('preInsert', this) :
model.emit('preUpdate', this);
this._isNew_internal = this.isNew;
next();
});
schema.post('save', function() {
var model = this.model(this.constructor.modelName);
model.emit('postSave', this);
this._isNew_internal ? model.emit('postInsert', this) :
model.emit('postUpdate', this);
this._isNew_internal = undefined;
});
schema.pre('remove', function (next) {
this.model(this.constructor.modelName).emit('preRemove', this);
next();
});
schema.post('remove', function() {
this.model(this.constructor.modelName).emit('postRemove', this);
});
};

Questions ?

François Zaninotto
@francoisz http://github.com/fzaninotto

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