JavaScript中使用Avalon duplex实现Checkbox全选逻辑

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title></title>
<style type="text/css">
  *{
    margin: 0;
    padding: 0;
  }
  #wrap{
    margin-left: 100px;
  }
  #wrap li{
    display: inline-block;
    *display: inline;
    zoom:1;
    vertical-align: middle;
  }
</style>
<script type="text/javascript" src='seed.js'></script>
</head>
<body>
  <div id='wrap' ms-controller='duplex'>
    <p><input type='checkbox' data-duplex-changed="select_all_cb" ms-duplex-checked='select_all'>全选</p>
    <ul>
      <li ms-repeat='list'>
        <input type='checkbox' ms-duplex-number="selected" ms-attr-value='el.id'>{{el.text}}
      </li>
    </ul>
    <p>选中项的id:{{selected}}</p>
  </div>
  <script type="text/javascript">
  require('avalon',function(avalon){
    var duplex=avalon.define('duplex',function(vm){
      vm.selected=[];//保存勾选的选项的id,方便传给后台
      vm.list=[{id:1,text:'aaa'},{id:2,text:'bbb'},{id:3,text:'ccc'},{id:4,text:'ddd'},{id:5,text:'eee'},{id:6,text:'fff'}];
      vm.select_all_cb=function(){//全选框change事件回调
        var list=duplex.list,selected=duplex.selected;
        if(this.checked){
          avalon.each(list,function(i,v){//循环保存着已经勾选选框的数据
            selected.ensure(v['id']);//如果里面没有当前选框的数据，就保存
          });
        }else
          selected.clear();//清空
      };
      vm.select_all=0;
    });
    duplex.selected.$watch('length',function(after){//监听保存数据数组的变化
      var len=duplex.list.length;      
      if(after==len)//子选框全部被勾选
        duplex.select_all=1;
      else//子选框有一个没有被勾选
        duplex.select_all=0;
    });
    avalon.scan();
  });
  </script>
</body>
</html>