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

Is (NaN >= 0) ?...... "I don't Know".

function IsNotNumber( i ){
    if( i >= 0 ){ return false; }
    if( i <= 0 ){ return false; }
    return true;
}

Conditions only execute if TRUE.

Not on FALSE.

Not on "I Don't Know".