js gets the root path of the web

function getRootPath (){
     //Get the current URL, such as: http://localhost:8090/jobservice/service/meun.jsp
 var curWwwPath=window.document.location.href ;
 //Get the directory after the host address, such as: jobservice/service/menu.jsp
 var pathName =window.document.location.pathname ;
 var pos=curWwwPath.indexOf (pathName) ;
 //Get the host address, such as: http://localhost:8090
 var localhostPaht =curWwwPath.substring ( 0 , pos) ;
 //Get the project name with "/", such as: /jobservice
 var projectName=pathName. substring ( 0 , pathName.substr(1).indexOf('/')+1);
return(localhostPaht+projectName);
}