Decorators Pattern using Books eStore

decorators.js

// Decorators Pattern
/*
We will create a Book Object with constructor to initialize Name,
Author, Ratings and Cost. 
Then we will add decorators to add feature to the Book object for
some Ebooks.
 */
 


 (function() {
    'use strict';

    // Creating the constructor to decorate
    function Book(name, author, cost) {
        this.name = name;
        this.author = author;
        this.cost = cost;
        this.ratings = [];
    }
    // Pushing methods to the prototype
    Book.prototype.addRating = function(rating) {
        this.ratings.push(rating);
        this.rating = this.ratings.reduce(function (p, c) {
            return p + c;
          }) / this.ratings.length;
        console.log('Average Rating: ' + this.rating )
    };
    Book.prototype.buy = function() {
        // Payment Routing
        console.log('Thank you for your order!')
    };

    var LOTR = new Book('LOTR', 'Tolkien', '1550');
    LOTR.addRating(3); // Average Rating: 3
    LOTR.addRating(5); // Average Rating: 4
    LOTR.addRating(5); // Average Rating: 4.333333333333333
    LOTR.addRating(4); // Average Rating: 4.25
    console.log(LOTR.rating); // 4.25
    LOTR.buy(); // Thank you for your order!



    
    var eBook = function(name, author, cost) {
        // Calling Book obj with name 
        Book.call(this, name);
        this.author = author;
        this.cost = cost;
        this.ratings = [];
    }
    /*
    We will use object.create to make a new object from Book's 
    prototype to our eBook's prototype so that we dont overwrite 
    Book's prototype.
     */ 
    eBook.prototype = Object.create(Book.prototype);

    eBook.prototype.buy = function() {
        console.log('Downloading Ebook...');
        Book.prototype.buy.call(this);
    };

    var HarryPotterEBook = new eBook('HP', 'Rowling', '3550');
    HarryPotterEBook.addRating(3); // Average Rating: 3
    HarryPotterEBook.addRating(5); // Average Rating: 4
    HarryPotterEBook.addRating(5); // Average Rating: 4.33
    HarryPotterEBook.addRating(4); // Average Rating: 4.25
    console.log(HarryPotterEBook.rating); // 4.25
    HarryPotterEBook.buy(); 
    /* Downloading Ebook...
    Thank you for your order! */




})();