为什么 JavaScript 中是“NaN”，我该如何解决？

Question

I have created a program that tells you a program that takes a number in JavaScript and tells you the various properties of that number.我创建了一个程序，它告诉您一个程序，该程序在 JavaScript 中接受一个数字并告诉您该数字的各种属性。

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8"/>
    </head>
    <body>
        <script>
            
            var div_sum = 0
            var num = Number(prompt('Please enter the number'))
            var pn_result = true
            for(var i = 2; i < num; i++){
                if(num % i === 0){
                    var pn_result = false
                    break
                }
            }
            if(pn_result){
                alert(String(num) + 'is a prime')
            } else {
                alert(String(num) + 'is not a prime\n' + String(num) + '=' + String(i) + 'x' + String(num / i))
            }
            var div_list = []
            for(var div = 1; div < num + 1; div++){
                if(num % div === 0){
                    div_list.push(div)
                }
            }
            var div_len = div_list.length
            alert('Number of divisor is' + String(div_len) )
            
            for(var i = 0; i < div_len + 1; i++){
                var div_sum = div_sum + div_list[i]
            }
            var div_sum = div_sum - num
            alert(div_sum)
        </script>
    </body>
</html>

At the end, I was curious if that number was a perfect number, so I output the sum of the divisor excluding myself.最后，我很好奇这个数字是否是一个完美的数字，所以我输出了不包括我自己的除数之和。

But the execution result came out as'NaN'.但是执行结果显示为'NaN'。

Oddly enough, the other operations did so in a finished state.奇怪的是，其他操作是在完成状态下完成的。 What is'NaN' and how do I fix it?什么是“NaN”，我该如何解决？

Answer 1

The main issue is this line.主要问题是这条线。 You are iterating 1 more time than the length of div_list .您比div_list的长度多迭代 1 次。

for(var i = 0; i < div_len + 1; i++){
  var div_sum = div_sum + div_list[i]
}

It should be它应该是

for(var i = 0; i < div_len; i++){
  var div_sum = div_sum + div_list[i]
}

Other issues include declaring redeclaring div_sum inside the for loop , and again immediately outside.其他问题包括在for loop内部重新声明div_sum ，并立即在外部声明。 You should declare it only once, and then reassign new values to it as such.您应该只声明一次，然后重新为其分配新值。

var div_sum = 0;
for(var i = 0; i < div_len + 1; i++){
  div_sum = div_sum + div_list[i]
}
div_sum = div_sum - num;

And finally, you should also use camelCase to name JavaScript variables.最后，您还应该使用camelCase命名法来命名JavaScript变量。 That is the normal convention.这是正常的约定。 Instead, you are using the snake_case convention, which is not usually used in JavaScript land.相反，您使用的是snake_case约定，它通常不用于JavaScript 。

Answer 2

change this改变这个

for(var i = 0; i < div_len + 1; i++)
  {
    var div_sum = div_sum + div_list[i]
  }

to this and it will work对此，它会起作用

for(var i = 0; i < div_len; i++)
   {
     var div_sum = div_sum + div_list[i]
   }

为什么 JavaScript 中是“NaN”，我该如何解决？

问题描述

2 个解决方案

解决方案1
1 2020-09-12 06:11:11

解决方案2
0 2020-09-12 10:31:59

为什么 JavaScript 中是“NaN”，我该如何解决？

问题描述

2 个解决方案

解决方案1 1 2020-09-12 06:11:11

解决方案2 0 2020-09-12 10:31:59

解决方案1
1 2020-09-12 06:11:11

解决方案2
0 2020-09-12 10:31:59