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);
                }                
            }
        });
    },