JavaScript NaN错误循环

Question

我在运行此代码时收到一个NaN错误。我一直在试图找出为什么现在有一段时间，不能为我的生活。

为了澄清，我试图接受;

• 客户

• 应付总金额有多少客户在进入

  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

您需要在循环之前定义这两个变量：

var totalowed = 0; 
var totalcustomers = 0; 

当你分配值给他们，他们最初不确定的，这总是产生问题。

你可以看到下面的工作片段：

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 2

你是不是从提示转换字符串转换成整数。在这里看到：

您可以使用：

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

记住要提供一个基数值的parseInt功能的完整性。

How to get numeric value from a prompt box?

Answer 3

totalowed和totalcustomers在while循环声明，因此无法使用外面。您将需要在while循环外定义它们。