微信小程序radio-group 默认选中某一项

   <radio-group class="radio-group " bindchange="manNumSelect" >
        <label class="radio_click clearfix" wx:for="{{items}}" wx:key="key">
            <text> {{item.value}}</text>
            <radio class="radio" color='#09f' value="{{item.value}}" checked="{{item.checked}}"/>           
        </label>
</radio-group>

 items: [
      {value: '1人',checked:"true"},
      {value: '2人'},
      {value: '3人'},
      {value: '4人'},
      {value: '5人'},
      {value: '6人'},
      {value: '7人'},
      {value: '8人'},
      {value: '9人'},
      {value: '10人'},
      {value: '10人以上'},
    ]

var index=6  //此处可以选择设置 需要选中的下标
this.data.items[index].checked="true"
    this.setData({
      items: this.data.items
    })