[JavaScript] 取url的hostname

取url的hostname

<script language="JavaScript" type="text/JavaScript">
function openup()
{
var url=getUrlHost();
url=url+"/SYXX/SYXX/WebAnnex/scienceNewUp.aspx?id=3004";
window.parent.mainFrame.location.href=url;
}
function openmod()
{
var url=getUrlHost();
url=url+"/SYXX/SYXX/WebAnnex/scienceNewMod.aspx?id=3004";
window.parent.mainFrame.location.href=url;

}
function getUrlHost()
{
 return 'http://'+window.parent.location.hostname+'/';


}
</script>