JavaScript获取当前请求参数值

<script type="text/javascript">
function GetQueryString(name){
var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)","i");
var r = window.location.search.substr(1).match(reg);
if (r!=null)
return unescape(r[2]);
return null;
}
alert(GetQueryString('url'));
</script>