全部的内容在下面网址中: https://goo.gl/I2sbES 我看不太懂这题目的意思和指示 希望高手路过能指点一下 <(_ _)> ============================ 题目如下: 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?!" 指示: 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. 题目要我们修改的原始码: var cashRegister = { total:0, //Dont forget to add your property add: function(itemCost) { this.total += 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 }; 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 //Show the total bill console.log('Your bill is '+cashRegister.total); --

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