flex 获取浏览器根路径

/**获取浏览器根路径*/
private function getContext():String
{
var bm:IBrowserManager = BrowserManager.getInstance();
bm.init();
var urlPrefix:String="http://"+URLUtil.getServerNameWithPort(bm.url)+"/";
var suffix:String=bm.url.replace(urlPrefix,"");
var context:String=suffix.substring(0,suffix.indexOf("/"));
return urlPrefix+context;
}