Factorial

<script type="text/javascript">

function factorial(int n)
{
    if(n == 0 || n == 1) return 0;
    else if(n>1) return n*factorial(n-1);
}
 var fac = 0;
 var R=prompt("Factorial de que numero? ");
 fac = factorial(R);
 document.write(""+fac);

</script>