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

NaN === NaN;        // false
Number.NaN === NaN; // false
isNaN(NaN);         // true
isNaN(Number.NaN);  // true

Equality operator (== and ===) cannot be used to test a value against NaN.

Look at Mozilla Documentation The global NaN property is a value representing Not-A-Numbe

The best way is using 'isNaN()' which is buit-in function to check NaN. All browsers supports the way..