<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <button @click="addAttribute()">添加屬性方法</button>  
        <p>student屬性顯示在下面</p>
        <ul>
            <li v-for="item in student">{{item}}</li>
        </ul>
    </div>
    <script src="./js/vue.js"></script>
    <script>
        new Vue({
            el: '#app',
            data: {
                student: {
                    name: 'zdx'
                }
            },
            methods: {
                addAttribute() {   
                    this.student.age = 18;    //為student對象添加屬性
                    console.log(this.student);
                }
            }
        })
    </script>
</body>
</html>

原因是由于受JavaScript的限制，vue.js不能監(jiān)聽對象屬性的添加和刪除，因為在vue組件初始化的過程中，會調(diào)用getter和setter方法，所以該屬性必須是存在在data中，視圖層才會響應(yīng)該數(shù)據(jù)的變化，針對這個問題

有兩種解決方案

1.this.$set(obj, key, value) 或 vue.set(obj, key, value)

methods: {
    addAttribute() {
        // this.student.age = 18;
        this.$set(this.student, 'age', 18);
        console.log(this.student);
    }
}

2.Object.assign(target, sources)

 methods: {
      addAttribute() {
          // this.student.age = 18;
          // this.$set(this.student, 'age', 18);
          this.student.age = 18;
          this.student = Object.assign({}, this.student);
          console.log(this.student);
      }
  }