overview on classes and objects in JS

class-objects-js

// the original Animal class and sayName method
function Animal(name, numLegs) {
    this.name = name;
    this.numLegs = numLegs;
}

Animal.prototype.sayName = function() {
    console.log("Hi my name is " + this.name);
};

// define a Penguin class
function Penguin(name) {
    this.name = name; // unique for each penguin
    this.numLegs = 2; // all penguins have 2 legs, so we set this
}

// set its prototype to be a new instance of Animal
Penguin.prototype = new Animal(); // inherits from Animal class

var penguin = new Penguin('pingu');
penguin.sayName(); // => Hi my name is Pingu
// check what properties and methods the child class has
// prototype chain


// private properties
function Person(first,last,age) {
   this.firstname = first;
   this.lastname = last;
   this.age = age;
   var bankBalance = 7500; // private variable

   this.getBalance = function() { // access the private variable
      return bankBalance;
   };
}

var john = new Person('John', 'Bravo', 33);
// try to print his bankBalance
console.log(john.bankBalance); // => undefined

var myBalance = john.getBalance();
console.log(myBalance); // => 7500


// private methods
function Person(first,last,age) {
   this.firstname = first;
   this.lastname = last;
   this.age = age;
   var bankBalance = 7500;
  
   var returnBalance = function() {
      return bankBalance;
   };

   this.askTeller = function() {
       return returnBalance;
   }
}

var john = new Person('John','Smith',30);
console.log(john.returnBalance); // => undefined
var myBalanceMethod = john.askTeller(); // => returnBalance
var myBalance = myBalanceMethod();
console.log(myBalance); // => 7500



// sample cash register app
function StaffMember(name,discountPercent){
    this.name = name;
    this.discountPercent = discountPercent;
}

var sally = new StaffMember("Sally",5);
var bob = new StaffMember("Bob",10);

// Create yourself again as 'me' with a staff discount of 20%
var me = new StaffMember('Gab', 20);

var cashRegister = {
    total:0,
    lastTransactionAmount: 0,
    add: function(itemCost){
        this.total += (itemCost || 0);
        this.lastTransactionAmount = itemCost;
    },
    scan: function(item,quantity){
        switch (item){
        case "eggs": this.add(0.98 * quantity); break;
        case "milk": this.add(1.23 * quantity); break;
        case "magazine": this.add(4.99 * quantity); break;
        case "chocolate": this.add(0.45 * quantity); break;
        }
        return true;
    },
    voidLastTransaction : function(){
        this.total -= this.lastTransactionAmount;
        this.lastTransactionAmount = 0;
    },
    // Create a new method applyStaffDiscount here
    applyStaffDiscount: function(employee) {
        return this.total -= this.total * (employee.discountPercent / 100);
    }
};

cashRegister.scan('eggs',1);
cashRegister.scan('milk',1);
cashRegister.scan('magazine',3);
// Apply your staff discount by passing the 'me' object 
// to applyStaffDiscount
cashRegister.applyStaffDiscount(me);

// Show the total bill
console.log('Your bill is '+cashRegister.total.toFixed(2));