using isNaN to evaluate input

Question

I am using isNaN to evaluate input in text box my function is like this

function IsNumeric(n) {
    return !isNaN(n);
}

it's working fine with numeric but not on negative values nor decimal values like 1.2,

but I will not accept negative or decimal values like 1.2

how can I do that?

Thanks

n is any type text in text box.... – air Feb 02 '11 at 14:29 — air, Feb 02 '11 at 14:29

score 3 · Accepted Answer · answered Feb 02 '11 at 14:33

3

You mean

function IsPostiveInteger(n) {
  var n = new Number(n);
  return !isNaN(n) && n===parseInt(n,10) && n>0;
}

answered Feb 02 '11 at 14:33

mplungjan

169,008
28
173
236

3

Actually the === is correct - it means that n not only has the same value but is the same type, e.g. an integer. http://stackoverflow.com/questions/359494/javascript-vs-does-it-matter-which-equal-operator-i-use – mplungjan Feb 02 '11 at 14:58

score 2 · Answer 2 · answered Feb 02 '11 at 14:32

2

Try to use Number(n). This will return NAN if its not a number. Else will return the same number irrespective of negative or positive

answered Feb 02 '11 at 14:32

Sachin Shanbhag

54,530
11
89
103

Brad Christie · Answer 3 · 2011-02-02T14:42:50.433

1

~~Shorter~~ Alternate solution:

function IsNumeric(n){
    // any valid number
    //return /^-?\d+(?:\.\d+)?$/.test(n);

    // only positive numbers
    //return /^\d+(?:\.\d+)?$/.test(n);

    // only positive whole numbers
    return /^\d+$/.test(n);
}

edited Feb 02 '11 at 14:42

answered Feb 02 '11 at 14:33

Brad Christie

100,477
16
156
200

But the asker does not want decimals nor negative values – mplungjan Feb 02 '11 at 14:42
@mplungjan: Yea, I was playing around with it after I saw the other's answers. Now It will only accept whole numbers. (as shown [on jsfiddle](http://www.jsfiddle.net/bradchristie/VeXQP/)) – Brad Christie Feb 02 '11 at 14:47
You mean as in 99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 – mplungjan Feb 02 '11 at 15:00

using isNaN to evaluate input

3 Answers3