sample javascript event

<html>
<head>
<script type="text/javascript">

function hitung_total(id, jumlah_ros_id){
        var total = 0;

        var input_element = document.getElementById(id);
        var key_total = id.split("#");

        total = parseInt(input_element.value) + parseInt(jumlah_ros_id);
        //total = input_element.value * jumlah_ros_id;  jika perkalian

        if (isNumber(total)) {
                document.getElementById("total#"+key_total[1]).innerHTML = total;
        }
        hitung_grand_total();
}

function hitung_grand_total() {
        var grand_total = 0;
        var total = document.getElementsByName("total");

        for (i = 0; i < total.length; i++) {

                if (isNumber(total[i].innerHTML)) {
                        grand_total += parseInt(total[i].innerHTML);
                }
        }

        document.getElementById("grand_total").innerHTML = grand_total;
}

function isNumber(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}

</script>
</head>
<body>
<div style="width:390px;">
produk1:  <span>10</span>
Lama Tayang: <input type="text" id="lama_tayang#0" onkeyup="hitung_total(this.id, 10)" />
Total <span id="total#0" name="total">10</span><br/>

produk2:  <span>20</span>
Lama Tayang: <input type="text" id="lama_tayang#1" onkeyup="hitung_total(this.id, 20)" />
Total <span id="total#1" name="total">20</span><br/>

<br/><br/>
<div style="float:right;">Grand Total : <span id="grand_total">30</span></div>

</div>

</body>
</html>