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

function isNotANumber(n) {
  if (typeof n !== 'number') {
    return true;
  } 
  return n !== n;
}