Sort:  

In JavaScript, false and 0 are not strict equally. Since it’s not a strong typed language, isNaN will considere 0 and return as false. Nowadays you can use isNumber to strictly check that. It’s safer.

Yes. What really made me want to throw a fit was when an empty string passed. I used isNumber()

LOL, no I didn't ...

Screenshot of JavaScript console showing ! isNaN() in use