treePanel的tbar的问题？

var tree=new Ext.tree.TreePanel({
        title:'我的树',
        root:root,
        renderTo:'treeview',
        loader:loader,
        tbar:[{new Ext.form.ComboBox({  //the line 29
                store:new Ext.data.SimpleStore({data:[[1,'用户名'],[2,'设备名']],fields:['id','name']}),
                mode:'local',
                displayField:'name',
                valueField:'id',
                triggerAction:'all'
            })      
        },{text:'搜索',handler:function(){}}]
    });
//为何下拉框不显示,浏览器报错,29行缺少标识符、字符串或数字