How do you check that a number is NaN in JavaScript?

Question

I’ve only been trying it in Firefox’s JavaScript console, but neither of the following statements return true:

parseFloat(\'geoff\') == NaN;

parseFloat(\'ge         


        

Answer 1

It seems that isNaN() is not supported in Node.js out of the box.
I worked around with

var value = 1;
if (parseFloat(stringValue)+"" !== "NaN") value = parseFloat(stringValue);