The Flyweight pattern

flyweight.js

// Flyweight.js - Copyright Addy Osmani, 2012.
// Consider public domain
// My implementation in JS of this:
// http://en.wikipedia.org/wiki/Flyweight_pattern

// Simulate pure virtual inheritance/'implement' keyword for JS
Function.prototype.implementsFor = function (parentClassOrObject) {
    if (parentClassOrObject.constructor == Function) {
        // Normal Inheritance 
        this.prototype = new parentClassOrObject;
        this.prototype.constructor = this;
        this.prototype.parent = parentClassOrObject.prototype;
    } else {
        // Pure Virtual Inheritance 
        this.prototype = parentClassOrObject;
        this.prototype.constructor = this;
        this.prototype.parent = parentClassOrObject;
    }
    return this;
}


// Flyweight object
var CoffeeOrder = {

    // Interfaces
    serveCoffee: function (context) {},
    getFlavor: function () {}

};


// ConcreteFlyweight object that creates ConcreteFlyweight 
function CoffeeFlavor(newFlavor) {

    var flavor = newFlavor;

    // If an interface has been defined for a feature
    // implement the feature
    if (typeof this.getFlavor === "function") {
        this.getFlavor = function () {
            return flavor;
        };
    }

    if (typeof this.serveCoffee === "function") {
        this.serveCoffee = function (context) {
            console.log("Serving Coffee flavor " + flavor + " to table number " + context.getTable());
        };
    }

}


// Implement interface for CoffeeOrder
CoffeeFlavor.implementsFor(CoffeeOrder);


// Handle table numbers for a coffee order
function CoffeeOrderContext(tableNumber) {

    var tableNumber = tableNumber;

    return {
        getTable: function () {
            return tableNumber;
        }
    }
}



//FlyweightFactory object
function CoffeeFlavorFactory() {
    var flavors = [];

    return {
        getCoffeeFlavor: function (flavorName) {

            var flavor = flavors[flavorName];
            if (flavor === undefined) {
                flavor = new CoffeeFlavor(flavorName);
                flavors.push([flavorName, flavor]);
            }
            return flavor;
        },

        getTotalCoffeeFlavorsMade: function () {
            return flavors.length;
        }
    }
}

// Sample usage:
// testFlyweight()
function testFlyweight() {


    // The flavors ordered. 
    var flavors = new CoffeeFlavor(),

        // The tables for the orders. 
        tables = new CoffeeOrderContext(),

        // Number of orders made
        ordersMade = 0,

        // The CoffeeFlavorFactory instance
        flavorFactory;

    function takeOrders(flavorIn, table) {
        flavors[ordersMade] = flavorFactory.getCoffeeFlavor(flavorIn);
        tables[ordersMade++] = new CoffeeOrderContext(table);
    }

    flavorFactory = new CoffeeFlavorFactory();

    takeOrders("Cappuccino", 2);
    takeOrders("Cappuccino", 2);
    takeOrders("Frappe", 1);
    takeOrders("Frappe", 1);
    takeOrders("Xpresso", 1);
    takeOrders("Frappe", 897);
    takeOrders("Cappuccino", 97);
    takeOrders("Cappuccino", 97);
    takeOrders("Frappe", 3);
    takeOrders("Xpresso", 3);
    takeOrders("Cappuccino", 3);
    takeOrders("Xpresso", 96);
    takeOrders("Frappe", 552);
    takeOrders("Cappuccino", 121);
    takeOrders("Xpresso", 121);

    for (var i = 0; i < ordersMade; ++i) {
        flavors[i].serveCoffee(tables[i]);
    }
    console.log(" ");
    console.log("total CoffeeFlavor objects made: " + flavorFactory.getTotalCoffeeFlavorsMade());
}