javascript中怎么产生一个随即数

javascript中怎么产生一个随即数刷新网页对话框

Math.random()

例：

function additional(id)
    {
        var result = window.showModalDialog("additional_customer_info.aspx?id="+id+"&r="+Math.random(), "", "help:no;resizable:no;status:no;center:yes;dialogWidth:840px;dialogHeight:600px;");
        location.href='updatecustomer.aspx';
    }
</script>