Vue监视数据的原理详解

		(1). 调用原生对应的方法对数组进行更新。

		(2). 重新解析模板，进而更新页面。

 <div id="root">
        <h2>人员信息</h2>
        <button @click="updatep">点击更新马东梅的信息</button>
        <ul>
            <li v-for='p in person' :key="p.id">
                {{p.name}} -- {{p.age}} -- {{p.gender}}
            </li>
        </ul>
        <button @click="addNew">在结尾添加一个人的信息</button>
    </div>

    <script>
        Vue.config.productionTip = false
        let vm = new Vue({
            el: '#root',
            data: {
                person: [
                    { id: "001", name: "马冬梅", age: 20, gender: "女" },
                    { id: "002", name: "夏洛特", age: 33, gender: "男" },
                    { id: "003", name: "沈腾", age: 50, gender: "男" },
                    { id: "004", name: "贾玲", age: 45, gender: "女" },
                ]
            },
            methods: {
                updatep() {            
                    // 但是下面方法不奏效,此方法Vue检测不到,
                    // 原因是因为数组上面没有getter和setter方法所以检测不到数据发生改变
                    // this.person[0] = {id:"001",name:"李焕英",age:66,gender:"女"}

                    // 下面方法奏效，是因为属性上面已经配置了getter和setter方法
                    // this.person[0].name = "李焕英"
                    // this.person[0].age = "66"
                    // this.person[0].gender = "女"

                    //  this.person.splice(0, 1, { id: "001", name: "李焕英", age: 66, gender: "女" }) 

                    this.$set(this.person, 0, { id: "001", name: "李焕英", age: 66, gender: "女" })
                },
                addNew() {
                    this.person.push({id: "005", name: "老妹啊", age: 99, gender: "女"})
                }
            },

        })
    </script>

<div id="root">
        <h2>学生信息</h2>
        <p>姓名：{{student.name}}</p>

        <!-- 
            一个很重要的点：如果是查找对象中不存在的属性，返回的是一个undefined
            不管v-show或者是v-if，如果等到undefined的就不显示
         -->
        <p v-show="student.sex">性别：{{student.sex}}</p>
        <p>年龄：{{student.age}}</p>
        <p>地址：{{student.address}}</p>
        <p>联系方式：{{student.contact}}</p>
        朋友：<p v-for="(v,index) in student.friends" :key="index">{{v.name}} -- {{v.age}}</p>
        <button @click="add">点击添加性别</button>
    </div>

    <script>
        Vue.config.productionTip = false
        let vm = new Vue({
            el: '#root',
            data: {
                student: {
                    name: "Jack",
                    age: 18,
                    address: "北京",
                    contact: "13xxxxxxx56",
                    friends: [
                        { name: 'Mark', age: 12 },
                        { name: 'Lisa', age: 52 },
                        { name: 'Guli', age: 25 },
                    ]
                }
            },
            methods: {
                add() {
                两种写法都可以
                    // this.$set(vm.student,"sex","男")
                    Vue.set(this.student,"sex","男")
                }
            },
        })
    </script>