isNaN() method.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>isNaN()</title>
</head>
<body>
    <script>
        var a = "Hello";
        if(isNaN(a)){
            document.write("Not a Number");

        }
        else{
            document.write("legal Number");
        }
    </script>
    
</body>
</html>