Live Demo: Armstrong number of three digits in JavaScript

<!DOCTYPE html>
<html>
  <body>
   <script>
    function Armstrong() {
        var r,sum=0,n,copy;
        n = parseInt(prompt("enter a number:"));
	    copy=n;
        while (copy>0) {
           r=copy%10;
   	       sum=sum+(r*r*r);
   	       copy=parseInt(copy/10);
        }
	if(n==sum)
	{
       document.write(n+" is a Armstrong number");
	}
	else
	{
	   document.write(n+" is not Armstrong a number");
	}
   }
    </script>
    <form>
      <input type="button" value="ArmstrongNo" onclick="Armstrong();" />
    </form>
  </body>
</html>