javascript获取网站根目录

function getRootPath(){ 
 var strFullPath=window.document.location.href; 
 var strPath=window.document.location.pathname; 
 var pos=strFullPath.indexOf(strPath); 
 var prePath=strFullPath.substring(0,pos); 
 var postPath=strPath.substring(0,strPath.substr(1).indexOf('/')+1); 
 return(prePath+postPath); 
 }