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

Simply convert the result to String and compare with 'NaN'.

var val = Number("test");
if(String(val) === 'NaN') {
   console.log("true");
}