Getting NaN error as the result

Question

I seem to be getting a NaN error as the result in my JavaScript code.

I'm pretty new to this, would appreciate any help.

Solved by giving value to the total var.

Possible duplicate of [How to get numeric value from a prompt box?](http://stackoverflow.com/questions/17907455/how-to-get-numeric-value-from-a-prompt-box) — Liam, Dec 16 '15 at 08:16
Just initialize your `total` to `0`. So that when you do a `total +=` then `total` has something to add to. — Abhitalks, Dec 16 '15 at 08:18
At least 3 different issues then, maybe try [How can I debug my JavaScript code?](http://stackoverflow.com/questions/988363/how-can-i-debug-my-javascript-code) — Liam, Dec 16 '15 at 08:19
You don't need to edit the question after you have got the answer. Pls revert your last edit, so that others can get any similar help. (We all know that your problem is solved, after you have accepted an answer.) — Tᴀʀᴇǫ Mᴀʜᴍᴏᴏᴅ, Dec 16 '15 at 08:52

simonzack · Accepted Answer · 2015-12-16T08:23:13.963

2

There are a couple of problems:

You should use parseFloat instead of using strings.
You should initialize total (this is what causes the nan)
You should initialize arrays properly.

function tax() {
    var price = new Array(10);
    var quant = new Array(10);
    var taxam = 18;
    var total = 0;
    for(i=0;i<10;i++) {
        quant[i] = parseFloat(prompt("Insert Quantity: "));
        price[i] = parseFloat(prompt("Insert Price: "));
    }
    for(i=0;i<10;i++) {
        total += price[i] * quant[i];
    }
    total = total * (taxam / 100);
    alert(total);
}

edited Dec 16 '15 at 08:23

answered Dec 16 '15 at 08:12

simonzack

19,729
13
73
118

1

Well, `"10" * "10"` is still `100`, multiplying numeric strings make perfect sense. – adeneo Dec 16 '15 at 08:15
@adeneo Thanks that's a js quirk I wasn't aware of, I think he's problem is not initializing `total`. Do you happen to know if this quirk exists in strict mode? – simonzack Dec 16 '15 at 08:18
@Normal_Dude_LearnsCode No problems you can accept it if it helped. – simonzack Dec 16 '15 at 08:23

score 1 · Answer 2 · answered Dec 16 '15 at 08:16

1

I guess with this var price = [10] you were trying to create an array with 10 numbers, but that is not the way it works in Javascript var price = [10] will give you an array with 10 at the 0th position. The only other tweak I would make there is make var price = [1,2,3,4,5,6,7,8,9,10] to actually achieve what you set out for initally

answered Dec 16 '15 at 08:16

Ade

181
1
1
14

Or `var price = new Array(10);` – Liam Dec 16 '15 at 08:18

score 0 · Answer 3 · answered Dec 16 '15 at 08:23

First of all, JavaScript is not Java ;)

You seem to try to initialize your arrays with a length of 10. This works in Java but in Javascript an array is dynamic and writing :

myArray = [10];

will just set the value 10 in the first index of the array.

Then, as you prompt the user to input numbers, the numbers will be interpreted as a string. So it would be good to cast it to a number before working with it. To cast it :

var value = '10000';
valueAsInt = parseFloat('10000',10);
//or simply 
valueAsInt = +value;

Now we come to your problem, as total is not initialised, the first affectation will be

undefined += n;

this will give a NaN.

So just initialise total before using it :

var total = 0;

score 0 · Answer 4 · answered Dec 16 '15 at 08:25

0

you have to initialize total variable first because it is undefined initially

var total = 0;

answered Dec 16 '15 at 08:25

ojus kulkarni

1,877
3
25
41

score -1 · Answer 5 · answered Dec 16 '15 at 08:15

You have to parse the String variables to a Number:

function tax() {

var price = [10];
var quant = [10];
var taxam = 18;
var total = 0;

 for(i=0;i<10;i++) {

    quant[i] = Number(prompt("Insert Quantity: "));

    price[i] = Number(prompt("Insert Price: "));

    }

for(i=0;i<10;i++) {

total += price[i] * quant[i];

 }

total = total * (taxam / 100);

alert(total);


}
tax()

Getting NaN error as the result

5 Answers5