Question

运行此代码时收到NaN错误。我一直试图找出原因，但不能为我的生活做好准备。

澄清一下，我想收到;

客户欠款总额

输入了多少客户

function Summarise()
{

    ID = prompt("Enter a Customer ID number ", -1)

    while(ID != -1) 
    {
        var gasUsed = 0
        var total = 0
        gasUsed = prompt("Enter amount of gas used ", "0")
        ///Standard Rate is used to assist in the calculation of customers in excess of 60 Gas Used
        StandardRate = 60 * 1.75

        if(gasUsed <= 60) 
        {
            total= gasUsed * 2
            document.write("Customers ID: " + ID)
            document.write(" has gas usage of " + gasUsed)
            document.write(" and owes $" + total)
            document.write("<br/>")
        } 
        else 
        {
            total= (gasUsed - 60) * 1.50 + StandardRate
            document.write("Customers ID: " + ID)
            document.write(" has gas usage of " + gasUsed)
            document.write(" and owes $" + total)
            document.write("<br/>")

        }

        var totalowed = total + totalowed
        var totalcustomers = ++totalcustomers

        ID = prompt("Enter a Customer ID number ", -1)

    }

    document.write("Total amount owed $" + totalowed)
    document.write("<br/>")
    document.write("Total Number of customers:" + totalcustomers)


}

Answer 1

totalowed和totalcustomers在while循环中声明，因此在其外部不可用。您需要在while循环之外定义它们。

Answer 2

您需要在循环之前定义这两个变量：

var totalowed = 0;
var totalcustomers = 0;

当你为它们分配值时，它们最初是未定义的，这总是会产生问题。

您可以在下面看到工作代码段：

function Summarise() {

ID = prompt("Enter a Customer ID number ", -1)
var totalowed = 0;
var totalcustomers = 0;
while(ID != -1) 
{
    var gasUsed = 0;
    var total = 0;
    gasUsed = prompt("Enter amount of gas used ", "0");
    ///Standard Rate is used to assist in the calculation of customers in excess of 60 Gas Used
    StandardRate = 60 * 1.75

    if(gasUsed <= 60) 
    {
        total = gasUsed * 2;
        document.write("Customers ID: " + ID);
        document.write(" has gas usage of " + gasUsed);
        document.write(" and owes $" + total);
        document.write("<br/>");
    } 
    else 
    {
        total= (gasUsed - 60) * 1.50 + StandardRate;
        document.write("Customers ID: " + ID);
        document.write(" has gas usage of " + gasUsed);
        document.write(" and owes $" + total);
        document.write("<br/>");

    }

    totalowed = total + totalowed;
    totalcustomers = ++totalcustomers;
    ID = prompt("Enter a Customer ID number ", -1);

}

document.write("Total amount owed $" + totalowed);
document.write("<br/>")
document.write("Total Number of customers:" + totalcustomers);
}

Summarise();

Answer 3

您没有将提示符中的字符串转换为整数。见这里：

您可以使用：

ID = parseInt(prompt("Enter a Customer ID number ", -1), 10);

请记住为parseInt函数提供基数值以确保完整性。

How to get numeric value from a prompt box?

JavaScript NaN错误循环

3 个答案: