function getRootPath() {
    //获取当前网址,如: http://localhost:8080/ems/Pages/Basic/Person.jsp
    var curWwwPath = window.document.location.href;
    //获取主机地址之后的目录,如: /ems/Pages/Basic/Person.jsp
    var pathName = window.document.location.pathname;
    var pos = curWwwPath.indexOf(pathName);
    //获取主机地址,如: http://localhost:8080
    var localhostPath = curWwwPath.substring(0, pos);
    //获取带"/"的项目名,如:/ems
    var projectName = pathName.substring(0, pathName.substr(1).indexOf('/') + 1);
    return(localhostPath + projectName);
}