js url parameter interception and closing browser tab method

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


function CloseWin(){
window.opener=null;
window.open('about:blank','_self');
window.close();
}