Extjs scope作用域的用法，方便的访问局部和外部变量

function newGrid(){        
        this.store = new Ext.data.Store({
                proxy : new Ext.data.HttpProxy({
                                url : url
                }),                        
                reader : reader        ,
                listeners : {
                        "load":function(store,records,option){
                                if(records.length>0)this.grid.selModel.selectFirstRow();//这里用this访问grid，如果没有下面的scope : this就访问不到
                        },
                        scope : this
                }
        });
         this.grid = new Ext.grid.GridPanel({
                cm:this.columnModel,
                store:this.store,
                region:'center',
                border:false,
                id:panelId,
                autoScroll:true,
                bbar:new Ext.PagingToolbar({store:this.store,pageSize:this.page,displayInfo:true})
        });
}