Javascript value returning not a number (NaN)

Question

I have a section of code as follows:

var percentageTemp =((parseInt(score)/parseInt(guesses))*100);
var percentage= percentageTemp.toFixed(2);

score and guesses are both set to 0 at the start of the code, and are altered as the user plays the game. The code works as it should, exept if I leave score variable 0, I get a NaN output. Why am I getting the NaN output when score = 0?

You should only get NaN when guesses is 0, your code will give 0 or "0.00" respectively when score is 0 — devnull69, May 05 '15 at 10:46
you can't divide zero by zero - hence the NaN as JavaScript can't quantify it. - http://www.math.utah.edu/~pa/math/0by0.html and a fiddle - https://jsfiddle.net/bLzsgd8q/ — Mark Walters, May 05 '15 at 10:47
Possible duplicate of http://stackoverflow.com/questions/18838301 — Sebastian Simon, May 05 '15 at 11:09

Quentin · Accepted Answer · 2015-05-05T10:52:05.193

3

The code works as it should, exept if I leave score variable 0, I get a NaN output.

You shouldn't do (examples from the Node.JS REPL):

> var score = 0; var guesses = 1; var percentageTemp =((parseInt(score)/parseInt(guesses))*100); var percentage= percentageTemp.toFixed(2); console.log(percentage)
0.00

If, on the other hand, you leave guesses at 0 then:

> var score = 0; var guesses = 0; var percentageTemp =((parseInt(score)/parseInt(guesses))*100); var percentage= percentageTemp.toFixed(2); console.log(percentage)
NaN

… because it isn't possible to divide by zero.

edited May 05 '15 at 10:52

answered May 05 '15 at 10:46

Quentin

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At least `0/0` will return `NaN`. Anything else `…/0` or `…/-0` will return `-Infinity` or `Infinity` depending on the sign of both numbers. – Sebastian Simon May 05 '15 at 11:17
Oh and `Infinity/Infinity` will return `NaN` as well. – Sebastian Simon May 05 '15 at 11:33

score 0 · Answer 2 · answered May 05 '15 at 11:06

I'd advise using a radix. parseInt(score, 10) to ensure the value doesn't get converted to hexadecimal. Also, note that javascripts handling of decimal numbers is not accurate. Try putting this in your console - (0.1 + 0.2) and see an unusual value returned - 0.30000000000000004

Javascript value returning not a number (NaN)

2 Answers2