js 立即对象 属性互访？

如题：
我想实现如下要求：

{
name:'name2',
[color=red]rowNum:this.items.length, [/color]
firstRowData:{address:'group2', tel:'1'},
[color=red]items:[[/color]
{address:'group2', tel:'2'},
{address:'group2', tel:'3'},
{address:'group2', tel:'4'}
]
},

[color=red]我想让rowNum的值为 items数组的元素个数。请问怎么实现！！[/color]

[color=red]我上面这样的方式，会包this.items不存在错误！！[/color]

var fn={
name:'name2',
rowNum:function(){
return this.items.length
}
firstRowData:{address:'group2', tel:'1'},
items:[
{address:'group2', tel:'2'},
{address:'group2', tel:'3'},
{address:'group2', tel:'4'}
]
}

这样可以获取，刚那个错了

直接量不存在this 一说

var fn={
name:'name2',
rowNum:fn.items.length,
firstRowData:{address:'group2', tel:'1'},
items:[
{address:'group2', tel:'2'},
{address:'group2', tel:'3'},
{address:'group2', tel:'4'}
]
},