is.number(NaN) returning true

[eriklharper]

Not sure why, but that is what is happening:

Running 0.4.0 of is_js

[didxga]

Hi @eriklharper, I think this has been fixed. Please check the latest version.

[jonhester]

#72 I actually fixed this last month.

console.log(typeof NaN) 
// number

It was decided that even though javascript considers NaN a number it goes against the point of the check so it now returns false for NaN.

[ekaradon]

Could you please also change then the return of is.nan?
Today, is.nan(null) return false, which means that null is considered as a number by the language. It is because javascript evaluated everything false as "0".
So you will always have values considered as number through NaN() when it is null, false or empty string.
I think the library is should remove this inconsistency from the language.

[ironmaniiith]

@ekaradon
For your statement, "is.nan(null) return false, which means that null is considered as a number by the language"

If is.nan returns false on something, that does not mean that it has to be a number.
NaN in javascript is a predefined keyword, which is neither equal to null, nor undefined and not even itself (yes..!!). But still, it is a number.
Hence it is correct if is.nan returns false for null.

console.log(NaN == NaN)
// false

Also is.nan will "only" return true when the argument passed is not equal to itself (to keep it simple, when NaN is passed as argument).
Hope that helps. :-)