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

You should use the global isNaN(value) function call, because:

• It is supported cross-browser
• See isNaN for documentation

Examples:

 isNaN('geoff'); // true
 isNaN('3'); // false

I hope this will help you.