Modules in node.js Modules in node.js

What do we mean by modules? What do we mean by modules? Files!

Disclamer Disclamer Opinionated Best Practices Opinionated Best Practices ahead ahead

The Module Layout The Module Layout

/** * @fileOverview Cors Middleware. */ var util = require('util'); var fs = require('fs'); var Promise = require('bluebird'); var _ = require('lodash'); var Middleware = require('./middleware'); var helpers = require('../util/helpers'); /** * The Cors Middleware. * */ var Cors = module.exports = {}; /** * CORS Middleware * * @param {Object} req The request Object. * @param {Object} res The response Object. * @param {Function(Error=)} next pass ctrl. */ Cors.use = function(req, res, next) { ... }; Module Description Dependencies System Deps NPM Deps Project Deps Export Statement Method Definition DocBlocks for Args Function Expression

The Dependencies The Dependencies @thanpolas 1. System Dependencies 2. NPM Dependencies 3. Project Dependencies /** * @fileOverview Cors Middleware. */ var util = require('util'); var fs = require('fs'); var Promise = require('bluebird'); var _ = require('lodash'); var Middleware = require('./middleware'); var helpers = require('../util/helpers'); 1. 2. 3.

The Module Types The Module Types

Constructors Constructors Objects Objects Only 2 types of Modules Only 2 types of Modules

Module Types Module Types Constructors Constructors var Cors = module.exports = function(){ Middleware.apply(this, arguments); }; util.inherits(Cors, Middleware); Objects Objects var Cors = module.exports = {};

Module Types Module Types Constructor Constructor /** * The Cors Middleware. * * @contructor * @extends {cc.Middleware} */ var Cors = module.exports = function(){ Middleware.apply(this, arguments); }; util.inherits(Cors, Middleware); /** * CORS Middleware * * @param {Object} req The request Object. * @param {Object} res The response Object. * @param {Function(Error=)} next pass ctrl. */ Cors.prototype.allowCrossDomain = function(req, res, next) {...};

Module Types Module Types Module Module /** * The Cors Middleware. * */ var Cors = module.exports = {}; /** * CORS Middleware * * @param {Object} req The request Object. * @param {Object} res The response Object. * @param {Function(Error=)} next pass ctrl. */ Cors.use = function(req, res, next) { ... };

If you want state --> Ctor If you want inheritance --> Ctor Helpers / Util --> Obj Enums / Dicts --> Obj Config Files --> Obj When to use which When to use which It's all about the state It's all about the state

Module Inheritance Module Inheritance The classical way The classical way

Module Inheritance Module Inheritance The Classical way The Classical way var util = require('util'); var EventEmitter = require('events').EventEmitter; var MiddlewareBase = module.exports = function() { EventEmitter.apply(this, arguments); this.foo = 1; }; util.inherits(MiddlewareBase, EventEmitter); middleware-base.midd.js var util = require('util'); var MiddleWareBase = require('./middleware-base.midd'); var Cors = module.exports = function() { MiddlewareBase.apply(this, arguments); console.log(this.foo); // 1 }; util.inherits(Cors, MiddlewareBase); cors.midd.js

Beware of context Beware of context Cors.prototype.use = function(req, res, next) { // good doSomeAsync(this._handleAsync.bind(this)); // bad doSomeAsync(this._handleAsync); };

Beware of performance Beware of performance Cors.prototype.use = function(req, res, next) { while(true) { // highly repetitive operation // good var self = this; doSomeAsync(function(result) { self._handleAsync(result); }); // bad doSomeAsync(this._handleAsync.bind(this)); } };

Shameless Plug Time Shameless Plug Time CIP! CIP!

CIP CIP Classical Inheritance Pattern at its Best Classical Inheritance Pattern at its Best var util = require('util'); var EventEmitter = require('events').EventEmitter; var MiddlewareBase = module.exports = function() { EventEmitter.apply(this, arguments); this.foo = 1; }; util.inherits(MiddlewareBase, EventEmitter); Base Constructors vanilla var EventEmitter = require('events').EventEmitter; var cip = require('cip'); var CeventEmitter = cip.cast(EventEmitter); module.exports = CeventEmitter.extend(); Base Constructors using CIP

CIP CIP Classical Inheritance Pattern at its Best Classical Inheritance Pattern at its Best var util = require('util'); var MiddleWareBase = require('./middleware-base.midd'); var Cors = module.exports = function() { MiddlewareBase.apply(this, arguments); console.log(this.foo); // 1 }; util.inherits(Cors, MiddlewareBase); Child Constructors vanilla var MiddlewareBase = require('./middleware-base.midd'); var Cors = module.exports = MiddlewareBase.extend(function () { /* Ctor */ }); Child Constructors using CIP

CIP CIP Classical Inheritance Pattern at its Best Classical Inheritance Pattern at its Best var MiddlewareBase = require('./middleware-base.midd'); var MiddlewareTraits = require('./middleware-traits.midd'); var Cors = module.exports = MiddlewareBase.extend(function () { /* Ctor */ }); Cors.mixin(MiddlewareTraits); Mixins! var Cors = require('./cors.midd'); var SuperCors = module.exports = Cors.extend(function () { /* Ctor */ }); Inheritance Goes on...

CIP CIP /thanpolas/cip /thanpolas/cip

Thank you (here is where you applaud) Thanasis Polychronakis @thanpolas

Questions? Thanasis Polychronakis @thanpolas