vue如何利用defineProperty,watcher,compiler,observer 实现数据的双向绑定

<div id="mvvm-app">
    <input type="text" v-model="word">
    <p>{{word}}</p>
    <button v-on:click="sayHi">change model</button>
</div>

<script src="./js/observer.js"></script>
<script src="./js/watcher.js"></script>
<script src="./js/compile.js"></script>
<script src="./js/defineProperty.js"></script>
<script>
    var vm = new MVVM({
        el: ‘#mvvm-app‘,
        data: {
            word: ‘Hello World!‘
        },
        methods: {
            sayHi: function() {
                this.word = ‘Hi, everybody!‘;
            }
        }
    });
</script>