原生js双向数据绑定

<input type="text" id="aa"/>
<span id="bb">{{hello}}</span>
<script>
    var obj = {};
    Object.defineProperty(obj,'hello',{
        set:function(val){
            document.getElementById('bb').innerHTML = val;
            document.getElementById('aa').value = val;
        }
    });
    document.getElementById('aa').onkeyup = function(e){
        obj.hello = e.target.value;
    };
    obj.hello = "";
</script>