js checkbox 单选

//js
function SignCheck(cbox)
{
var obj = document.getElementsByTagName("input");
for (var i=0; i < obj.length; i++)
{
if(obj[i].type == "checkbox")
{
obj[i].checked = false;
}
var sid = cbox.id;
document.getElementById(sid).checked = true;
}
}

//checkbox
<input id="Checkbox1" type="checkbox" name="ck" onclick="SignCheck(this);" runat="server" />