提示计算器的结果以NaN为单位

Question

我是初学者，正在研究初学者的问题，但需要一些帮助

我正在尝试编写自己的小费计算器应用程序，但结果是NaN。

我确信这是一个简单的解决方法，但是我还没有看到问题所在。我的代码如下。有人可以告诉我我在做错什么，导致我的finalCost导致NaN而不是billAmount + tipTotal吗？

var billAmount = prompt('What is your total bill?');

var tipAmount = prompt('How much do you want to tip');

console.log(billAmount);

var tip = tipAmount / 100;

var tipTotal = tip * billAmount;

function finalCost(billAmount, tipTotal) {
  return billAmount + tipTotal;
};

console.log("The tip is " + tipTotal);
console.log("The total bill is " + finalCost());

Answer 1

太近了！您只是错过了将值传递到最终的计算方法中。

var billAmount = prompt('What is your total bill?');

var tipAmount = prompt('How much do you want to tip');

console.log(billAmount);

var tip = tipAmount/100;

var tipTotal = tip*billAmount;

function finalCost(billAmount, tipTotal) {
	return billAmount + tipTotal;
};

console.log("The tip is " + tipTotal);
console.log("The total bill is " + finalCost(billAmount, tipTotal));

您还可以删除参数，仅在计算中使用“全局”值

var billAmount = prompt('What is your total bill?');

var tipAmount = prompt('How much do you want to tip');

console.log(billAmount);

var tip = tipAmount/100;

var tipTotal = tip*billAmount;

function finalCost() {
	return billAmount + tipTotal;
};

console.log("The tip is " + tipTotal);
console.log("The total bill is " + finalCost());

Answer 2

还有一个问题。直接从float设置prompt()值并不能确保float值（默认情况下被视为string），因此将prompt()函数包装在{{ 1}}函数：

parseFloat()

这应该验证var billAmount = parseFloat(prompt('What is your total bill?')); var tipAmount = parseFloat(prompt('How much do you want to tip')); if(isNaN(billAmount) || isNaN(tipAmount)){ alert("Bill amount or Tip is Invalid"); } else { console.log("This bill is " + billAmount); var tip = tipAmount / 100; var tipTotal = tip * billAmount; console.log("The tip is " + tipTotal); console.log("The total bill is " + finalCost(billAmount, tipTotal)); } function finalCost(billAmount, tipTotal) { return billAmount + tipTotal; };和billAmount的值是tipAmount，并且如果不是，则阻止进一步执行。