Cash Register - using objects and methods

gistfile1.js

// Codeacademy.org project, "Cash Register"
// Note that you cannot change prices without changing the methods!
// A better project would ask the student to calculate the total bill using price and quantity as input.

function StaffMember(name,discountPercent){
    this.name = name;
    this.discountPercent = discountPercent;
}

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;
    },
    voidLastTranscation : function(){
        this.total -= this.lastTransactionAmount;
        this.lastTransactionAmount = 0;
    },
    // Create a new method applyStaffDiscount here
    applyStaffDiscount : function(employee) {
        this.total -= this.total * (employee.discountPercent/100);
    }
    
};