anchor.diff:        teacherselector.children.add(option1);
         print(classList[1][j]+"done");
       }
  +
  +    var path = 'http://127.0.0.1:8008/showmes';  //默认显示classList中第一个课程名的comments内容
  +    var httpRequest = new HttpRequest();
  +    httpRequest
  +      ..open('POST', path)
  +      ..send(JSON.encode(classList[0][0]))
  +      ..onLoadEnd.listen((e) => requestMesComplete(httpRequest));
  +
     } else {
       querySelector('#Myclassbt').text='nanguo';
     }
  
positive.code: String USERID;             //用于记录用户名（一直可以使用）
  var chooseclassTeacher,chooseclassCourse;           //用于记录选择的
  List classList = new List();
  List teacherList = new List();
  List twoList = new List();
  SelectElement classesselector = new SelectElement();
  SelectElement teacherselector = new SelectElement();
  
  
negative.code:   var index = teacherselector.selectedIndex;
    classesselector.options[index].selected = true;
    chooseclassTeacher = classesselector.options[index].firstChild.nodeValue;
  }
  
  void Modeshift(MouseEvent event){               ///转换到标签模式
  