Check for NaN, null and >=0 in one condition

Question

I have a var a;

Its value can be NaN, null and any +ve/-ve number including 0.

I require a condition which filters out all the values of a such that

Answer 1

I had the same problem some weeks ago, I solved it with:

if(~~Number(test1)>0) {
  //...
}

http://jsfiddle.net/pT7pp/2/

Answer 2

Ohk ...But i actually found the ans .. it is so Simple .

parseInt(null) = NaN.

So if(parseInt(a)>=0){} would do ...Yayyee

Answer 3

This seems to work well:

if (parseFloat(x) === Math.sqrt(x*x))...

Test:

isPositive = function(x) { return parseFloat(x) === Math.sqrt(x*x) }
a = [null, +"xx", -100, 0, 100]
a.forEach(function(x) { console.log(x, isPositive(x))})

Answer 4

NaN is not >= 0, so the only exclusion you need to make is for null:

if (a !== null && a >= 0) {
    ...
}

Answer 5

typeof x == "number" && x >= 0

This works as follows:

• null -- typeof null == "object" so first part of expression returns false
• NaN -- typeof NaN == "number" but NaN is not greater than, less than or equal to any number including itself so second part of expression returns false
• number -- any other number greater than or equal to zero the expression returns true

Answer 6

Since you tagged jQuery, take a look at $.isNumeric()

if($.isNumeric(a) && a >= 0)