49.名称案例-方式2.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="./lib/vue.js"></script>
</head>

<body>
    <div id="app">
        <!--1 我们要监听到文本框数据的改变， 这样才知道什么时候去拼接出一个fullName-->
        <!--2 如何监听到文本框数据的改变 keyup事件-->
        <!---->
        <input type="text" v-model="firstName" > +
        <input type="text" v-model="lastName" > =
        <input type="text" v-model="fullName">

    </div>
    <script>
        var vm = new Vue({
            el: '#app',
            data: {
                firstName: '',
                lastName: '',
                fullName: '',
            },
            methods: {
                getFullName() {
                    this.fullName = this.firstName + ' ' + this.lastName
                },
                getLastName() {
                    this.fullName = this.firstName + ' ' + this.lastName
                }
            },
            watch: {
                //使用这个而属性可以监听data中指定数据的变化，然后触发这个watch对应的function函数
                firstName: function(newVal, oldVal){
                    //this.fullName = this.firstName + ' ' + this.lastName
                    //this.fullName = newVal + ' ' +this.lastName
                },
                lastName: function(newVal){
                    this.fullName = this.firstName + ' ' +newVal
                },

            },

        })
    </script>
</body>

</html>