extjs动态插入一列

  StdDayWordQuery:function(btn,event){
         var form=Ext.getCmp('queryFormSDW');
         var userNameORuserCode = form.getForm().getValues()['userNameORuserCode'];
         var gradeCode = form.getForm().getValues()['gradeCode'];
         var startDate = form.getForm().getValues()['startDate'];
         var endDate = form.getForm().getValues()['endDate'];        

         var params="gradeCode="+gradeCode+'&';
         params+="userNameORuserCode="+userNameORuserCode+'&';
         params+="startDate="+startDate+'&';
         params+="endDate="+endDate;        

         Ext.Ajax.request({
             method : 'POST',
             url:'getDailyWordNum.action?'+params,
             async:false,
             success:function(response) {
                 var ret=Ext.decode(response.responseText);
 //                console.log(ret);
                 if(ret.success){
                     //eval("var res=" + response.responseText);
                     //var rows = res.rows;
                     var rows=Ext.decode(response.responseText).rows;
                     var cols = new Array();
                     var xx = new Array();
                     console.log(rows);
                     console.log(rows[0]);
                     for(var x in rows[0]){
                         //console.log(x);
                         cols.push(new Ext.grid.column.Column({
                             text: x,
                             dataIndex : x
                         }));
                         xx.push(x);
                     }
                     console.log(xx);
                     var store = new Ext.data.Store({
                         fields: xx,
                         data: rows
                     });
                     var grid = Ext.getCmp('StudentDayWordGrid');
                     grid.reconfigure(store,cols);
                 }
                 else{
                     Ext.Msg.alert("错误", ret.msg);
                 }
             }
         });
     },