JS获取工程的根路径

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);
}