Why is'NaN' in JavaScript and how do I fix it?
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.
<!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.
But the execution result came out as'NaN'.
Oddly enough, the other operations did so in a finished state. What is'NaN' and how do I fix it?
2 answers
solution1
1 2020-09-12 06:11:11
The main issue is this line. You are iterating 1 more time than the length of div_list .
for(var i = 0; i < div_len + 1; i++){
var div_sum = div_sum + div_list[i]
}
It should be
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. You should declare it only once, and then reassign new values to it as such.
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. That is the normal convention. Instead, you are using the snake_case convention, which is not usually used in JavaScript land.
solution2
0 2020-09-12 10:31:59
change this
for(var i = 0; i < div_len + 1; i++)
{
var div_sum = div_sum + div_list[i]
}
to this and it will work
for(var i = 0; i < div_len; i++)
{
var div_sum = div_sum + div_list[i]
}
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