I have some question


#1


https://www.codecademy.com/en/courses/close-the-super-makert/0/7?curriculum_id=506324b3a7dffd00020bf661#


In this program what is the use of this.total += (itemCost || 0) in our add method. I think it is working if i only write this.total += itemCost;
Also what is the use of this.lastTransactionAmount = 0; in "voidLastTransaction" method. It is working fine without this statement.
And what is the use of .toFixed(2) in console.log, in the last line of this program.

sorry for so many question but i think clearing every problems will make me a good programmer.


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("prince", 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) {
        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));


#2

true, but if you accidentally get a invalid item, without || 0 you might get an error, now, zero will be added instead. Sort of safeguard/insurance policy.

again, another safeguard. Sometimes, certain code can help your program to crash less easily.

this means you always get 2 digit output


#3

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