Question

我在这里遇到了一些麻烦。我检查以确保我的变量仅使用数字定义，但代码仍然返回而不是数字。谁知道我做错了什么？

以下代码：

//declare vars and/or constants
var endString = "Total cost per night is $";
var viewCost;
var discount;

//input vars
pplCount = prompt("How many people will be staying?");
discYes = prompt("Do you have an AAA discount?");
viewYes = prompt("Do you want a room with a view?");

//if variables

if(pplCount === "1" || pplCount === "2" && discYes === "Yes" && viewYes === "Yes") {
discount = 50 * 0.15;
roomCost = 50;
roomCost = +roomCost - discount + viewCost;
viewCost = (+roomCost * 0.10);
document.write(endString + roomCost);
}else if(pplCount === "3" || pplCount === "4" && discYes === "Yes" && viewYes === "Yes") {
discount = 60 * 0.10;
roomCost = 60;
roomCost = roomCost - discount + viewCost;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}
else if(pplCount === "5" || pplCount === "6" && discYes === "Yes" && viewYes === "Yes") {
discount = 70 * 0.05;
roomCost = 70;
roomCost = roomCost - discount + viewCost;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}

else if(pplCount === "1" || pplCount === "2" && discYes === "No" && viewYes === "Yes") {
discount = 50 * 0.15;
roomCost = 50;
roomCost = roomCost + viewCost;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}
else if(pplCount === "3" || pplCount === "4" && discYes === "No" && viewYes === "Yes") {
discount = 60 * 0.10;
roomCost = 60;
roomCost = roomCost + viewCost;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}
else if(pplCount === "5" || pplCount === "6" && discYes === "No" && viewYes === "Yes") {
discount = 70 * 0.05;
roomCost = 70;
roomCost = roomCost + viewCost;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}

else if(pplCount === "1" || pplCount === "2" && discYes === "No" && viewYes === "No") {
discount = 50 * 0.15;
roomCost = 50;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}
else if(pplCount === "3" || pplCount === "4" && discYes === "No" && viewYes === "No") {
discount = 60 * 0.10;
roomCost = 60;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}
else if(pplCount === "5" || pplCount === "6" && discYes === "No" && viewYes === "No") {
discount = 70 * 0.05;
roomCost = 70;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}

else if(pplCount === "1" || pplCount === "2" && discYes === "Yes" && viewYes === "No") {
discount = 50 * 0.15;
roomCost = 50;
roomCost = roomCost - discount;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}
else if(pplCount === "3" || pplCount === "4" && discYes === "Yes" && viewYes === "No") {
discount = 60 * 0.10;
roomCost = 60;
roomCost = roomCost - discount;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}
else if(pplCount === "5" || pplCount === "6" && discYes === "Yes" && viewYes === "No") {
discount = 70 * 0.05;
roomCost = 70;
roomCost = roomCost - discount;
viewCost = (roomCost * 0.10);
document.write(endString + roomCost);
}

是因为我两次定义roomCost吗？

Answer 1

NaN是Number操作提供无效结果（非数字）时获得的

像：

5 - "a"
5 + NaN
parseInt("a", 10)
5 + undefined

NaN 有毒，因为任何以NaN作为操作数的操作也会返回NaN。找出你操作不好的地方。

看着你的代码，我发现你用的是字符串而不是数字。使用parseInt()将字符串转换为正确的数字。如果parseInt返回NaN给出错误，请务必验证您的输入。

Answer 2

忽略你在这里做的其他顽皮的东西，你在一些地方使用viewCost而没有先定义它。（这是不是数字。）

将前几行更改为以下内容可解决问题：

//declare vars and/or constants
var endString = "Total cost per night is $";
var viewCost = 0;
var discount = 0;

Answer 3

var viewCost; // <---defined, but not assigned to

roomCost = +roomCost - discount + viewCost;
                                  ^^^^^^^^

当你第一次运行时，你只是声明了变量，但尚未分配它：

NaN显然是一个数字，或者是它？

3 个答案: