JS Demo III

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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("john",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 * ( 1 - employee.discountPercent/100 );   // emplyee.discountPercent
    }
    
};

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));

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wilber.shinobi的个人空间 引用 删除 wilber.shinobi   /   2015-08-21 15:50:36
Bleep Bleep
The boss looks down at his pager to see Register 8 needs assistance. They have scanned an item too many times and need to void the last transaction.

So he turns to you and says: "Okay JavaScript Ninja! What do we do now?!"

Instructions
We need to keep track of how much the last transaction was. Modify the add method to keep track of the amount of the last transaction. This should be tracked in a new property, lastTransactionAmount.

Add a method called voidLastTransaction that subtracts the last amount transacted from total.

Then use the new method to void the last item we scanned. Finally, scan only 3 of the same item instead.

?
Hint
Remember that when you add a property or method to an object in literal notation, you should follow it with a , (comma) unless it is the last item of the object.

How should you update lastTransactionAmount? Each time add runs, you should change the value of lastTransactionAmount to itemCost so that lastTransactionAmount always refers to the cost of the last transaction.
===========================
Code Sample:
var cashRegister = {
    total:0,
    //Dont forget to add your property
   
    add: function(itemCost) {
        var lastTransactionAmount = 0;  
        this.total +=  itemCost;
        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;
    },
    //Add the voidLastTransaction Method here
    voidLastTransaction : function() {
        this.total -= this.lastTransactionAmount;
    }
   
};

cashRegister.scan('eggs',1);
cashRegister.scan('milk',1);
cashRegister.scan('magazine',1);
cashRegister.scan('chocolate',4);

//Void the last transaction and then add 3 instead
cashRegister.voidLastTransaction();
cashRegister.scan('chocolate',3);

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

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