Ошибка в наследовании Prototype - JavaScript - Ответ 10063595

function Print(list){
    for (var i = 0; i < list.length; i++) {
        document.write("<p>" + list[i]);
    }
}
 
function CalculaitingGetCost(list) {
    function makeBuffer() {
        var globCost = 0;
 
        function makeS(somePurch) {
            if (somePurch == undefined) {
                return globCost;
            } else {
                return globCost = globCost + somePurch;
            }
        };
        makeS.reset = function () {
            globCost = 0;
        }
        return makeS;
    }
 
    var makeS = makeBuffer();
    for (i = 0; i < list.length; i++) {
        makeS(list[i].getCost());
    }
    document.write("<h2>You would pay: " + makeS().toFixed(2) + "</h2>");
 
    makeS.reset();
}
function Purchase(name, price, amount) {
    this._name = name;
    this._price = price;
    this._amount = amount;
}
 
Purchase.prototype.getCost = function(){
    return this._price * this._amount;
};
 
Purchase.prototype.toString = function (){
    return ('' + this._name + ';' + this._price.toFixed(2) + ';' + this._amount + ';' + this.getCost().toFixed(2));
}
 
var purch = [];
purch[0] = new Purchase('Telephone', 430, 1);
purch[1] = new Purchase('Computer', 600, 1);
purch[2] = new Purchase('Table', 78, 2);
purch[3] = new Purchase('Bottle', 5, 14);
 
Print(purch);
CalculaitingGetCost(purch);
 
 
function PercentDiscPurchase (name, price, amount, percent) {
    Purchase.apply(this, arguments);
    this._percent = percent;
 
    this.getCost = function ()
    {
        return (Purchase.prototype.getCost.apply(this) * (1-this._percent/100));
    }
 
    this.toString = function ()
    {
        return (Purchase.prototype.toString.apply(this) + ";" + this._percent);
    }
}
 
purch[4] = new PercentDiscPurchase('Bag', 120, 2, 30);
purch[5] = new PercentDiscPurchase('Pan', 3, 25, 50);
purch[6] = new PercentDiscPurchase('Keyboard', 80, 1, 10);
 
Print(purch);
CalculaitingGetCost(purch);
 
function StaticDiscPurchase(name, price, amount) {
    Purchase.apply(this, arguments);
    this.staticDiscount = 14;
}
 
StaticDiscPurchase.prototype = Object.create(Purchase.prototype);
StaticDiscPurchase.prototype.constructor = StaticDiscPurchase;
 
StaticDiscPurchase.prototype.getCost = function ()
{
    return (Purchase.prototype.getCost.apply(this) - this.staticDiscount);
}
StaticDiscPurchase.prototype.toString = function ()
{
    return (Purchase.prototype.toString.apply(this) + ";" +this.staticDiscount);
}
 
purch[7] = new StaticDiscPurchase('T-shot', 80, 3);
purch[8] = new StaticDiscPurchase('Ring', 1300, 1);
purch[9] = new StaticDiscPurchase('Schose', 370, 2);
 
Print(purch);
CalculaitingGetCost(purch);