JS如何获取RadiobuttonList的选中值

JS代码：

<script language="javascript" type="text/javascript">
function RadioButtonList1Changed() {
var vRbtid = document.getElementById("RadioButtonList1");
//得到所有radio
var vRbtidList = vRbtid.getElementsByTagName("INPUT");
for (var i = 0; i < vRbtidList.length; i++) {
if (vRbtidList[i].checked) {
var text = vRbtid.cells[i].innerText;
var value = vRbtidList[i].value;
alert("选中项的text值为" + text + ",value值为" + value);
}
}
}
</script>

HTML:

<asp:RadioButtonList ID="RadioButtonList1" runat="server" onClick="return RadioButtonList1Changed()">
<asp:ListItem>1</asp:ListItem>
<asp:ListItem>2</asp:ListItem>
<asp:ListItem>3</asp:ListItem>
</asp:RadioButtonList>