JavaScript Design Patterns

After reading Addy Osmani’s book ‘JavaScript design patterns’ , I thought I would summarize some of the patterns I found useful and have been using in some projects.It is an awesome book and has a lot of useful information for JavaScript framework developers.

Module pattern

The Module pattern encapsulates “privacy”, state and organization using closures. Itprovides a way of wrapping a mix of public and private methods and variables. With this pattern, only a public API is returned, keeping everything else within the closure private.

var myNamespace = (function () {
var myPrivateVar, myPrivateMethod;
myPrivateVar = 0;
myPrivateMethod = function( foo ) {
console.log( foo );
return {
myPublicVar: "foo",
myPublicFunction: function( bar ) {
myPrivateMethod( bar );

Revealing Module pattern

The revealing module pattern is an updated version of the module pattern where all functions and variables are declared in the private scope and an anonymous object with pointers to the private functionality is returned.

var myRevealingModule = (function () {
var privateVar = "this is private",
publicVar = "this is public";
function privateFunction() {
console.log( privateVar );
function publicSetName( strName ) {
privateVar = strName;
function publicGetName() {
// Reveal public pointers to private functions and properties
return {
setName: publicSetName,
greeting: publicVar,
getName: publicGetName

Prototype inheritance

JavaScript doesn’t support the concept of classes but it does support special constructor functions that work with objects. Functions in JavaScript have a property called a prototype. When we call a JavaScript constructor to create an object, all the properties of the constructor’s prototype are then made available to the new object.

function Car(model, year) {
this.model = model;
this.year = year;
Car.prototype.toString = function() {
return this.model + ", " + this.year;
var suzuki= new Car("Maruti 800",1983);

Singleton pattern

In JavaScript, Singletons serve as a shared resource namespace. The singleton pattern is used to restrict instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system.

function init() {
// Private methods and variables
function privateMethod(){
console.log( "I am private" );
var privateVariable = "Im private";
return {
// Public methods and variables
publicMethod: function () {
console.log( "The public can see me!" );
publicProperty: "I am public",
return {
// Get the Singleton instance if one exists
getInstance: function () {
if ( !instance ) {
instance = init();
return instance;
var singleA = mySingleton.getInstance();

Mixin inheritance

In JavaScript, we can look at inheriting from Mixins as a means of collecting functionality through extension. Each new object we define has a prototype from which it can inherit further properties.

var Person = function( firstName, lastName){
this.firstName = firstName;
this.lastName = lastname;
var clark = new Person("Clark", "Kent");
var Superhero = function(firstName,lastname, powers){
this.powers = powers;,firstName,lastName);
SuperHero.prototype = Object.create(Person.prototype);
var superMan = new Superhero( "Clark", "Kent", [ "flight", "strength" ]);

Facade pattern

This pattern provides a convenient higher-level interface to a larger body of code,hiding its true underlying complexity. jQuery uses facades for much of its API to simplify complex operations. An example is jQuery’s $(document).ready(..) method which internally, is powered by a method called bindReady() which performs some ofthe following, to simplify the job for us.

$(document).ready(function () {