javascript控制frame,iframe的src属性代码

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

function tiao()
{
var x_url=GetQueryString("theiframe").toString();
document.all.mainFrame.src=x_url;
}
//-->
</script>