Interview series [Java Script] : curious case of NaN

Have you ever tried to validate NaN using == or ===? could you correctly guess the output of below statements?

1. x=parseInt("string")
2. console.log(x)
3. x==NaN
4. x===NaN
5. NaN===NaN
6. isNaN(x)

well, if you correctly answerd all the statements then congtars, but if don't; don't worry, i will try to give a walk through. Let's first the output first -

x=parseInt("string")
NaN
console.log(x)
NaN
x==NaN
false
x===NaN
false
NaN===NaN
false
isNaN(x)
true

It is not possible to rely on the equality operators (== and ===) to determine whether a value is NaN or not, because both NaN == NaN and NaN === NaN evaluate to false. Hence, the necessity of an isNaN function.

source - http://droidscript.org

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