ExtJs表格没有显示数据

菜鸟求助，为什么下面的代码没有显示。求解。。
JS如下：Ext.onReady(function(){
  var cm = new Ext.grid.ColumnModel([
        {header:'编号',dataIndex:'id'},
        {header:'名称',dataIndex:'name'},
        {header:'描述',dataIndex:'descn'}
    ]);  var data = [
        ['1','name1','descn1'],
        ['2','name2','descn2'],
        ['3','name3','descn3'],
        ['4','name4','descn4'],
        ['5','name5','descn5']
    ];    var store = new Ext.data.Store({
        proxy:new Ext.data.MemoryProxy(data),
        reader:new Ext.data.ArrayReader([
                {name:'id'},
                {name:'name'},
                {name:'descn'}
            ])
    });    store.load();    var grid = new Ext.grid.GridPanel({
        renderTo:'grid',
        store:store,
        cm:cm
    });
});
HTML如下：<html>
<head>
　　　 <meta http-equiv="content-type" content="text/html; charset=utf-8">
<link rel="stylesheet" type="text/css" href="../../resources/css/ext-all.css">
<script type="text/javascript" src="../../adapter/ext/ext-base.js"></script>
<script type="text/javascript" src="../../ext-all-debug.js"></script>
<script type="text/javascript" src="Hello.js"></script>
<script type="text/javascript" src="../../source/locale/ext-lang-zh_CN.js"></script>
</head>
<body>
<div id='grid'></div>
</body>
</html>
结果如下：

解决方案 »

  1.   

    var cm = new Ext.grid.ColumnModel([
            {header:'编号',dataIndex:'id'},
            {header:'名称',dataIndex:'name'},
            {header:'描述',dataIndex:'descn'}
        ]);
    把这一部分放到
       var store = new Ext.data.Store({
            proxy:new Ext.data.MemoryProxy(data),
            reader:new Ext.data.ArrayReader([
                    {name:'id'},
                    {name:'name'},
                    {name:'descn'}
                ])
        });
    后面，dataIndex:''指向已经定义好的列，你都没定义，怎么使用