JavaScript NaN error loop

Question

I am receiving a NaN error when I run this code. I've been trying to find out why for a while now and can't for the life of me.

To clarify, I am trying to receive;

the total amount owed by customers

how many customers are entered

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)


}

This is because you are using some variable that is undefined and providing undefined value.. — DeDevelopers, Sep 29 '14 at 11:50
Im still very very new to JavaScript, can you explain a little more @ DeDevelopers — Ryan Miller, Sep 29 '14 at 11:57

score 0 · Answer 1 · answered Sep 29 '14 at 12:00

0

totalowed and totalcustomers are declared in the while loop and thus not available outside it. You will need to define them outside the while loop.

answered Sep 29 '14 at 12:00

FlorisLang

21
4

score 0 · Accepted Answer · answered Sep 29 '14 at 12:00

You need to define these two variables before the loop:

var totalowed = 0;
var totalcustomers = 0;

they were initially undefined when you were assigning values to them, this always create problems.

You can see the working snippet below:

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();

Thanks heaps, I see what you mean. Silly mistake on my part. — Ryan Miller, Sep 29 '14 at 12:06

score -1 · Answer 3 · edited May 23 '17 at 12:13

-1

You are not converting the string from the prompt into an integer. See here:

You can use:

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

Remember to provide a radix value to the parseInt function for completeness.

How to get numeric value from a prompt box?

edited May 23 '17 at 12:13

Community

1
1

answered Sep 29 '14 at 11:51

RichieAHB

2,030
2
20
33

JavaScript NaN error loop

3 Answers3