$watch使用

January 19, 2022
triumph

<!DOCTYPE html>
<html lang="zh-CN">

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

<body>
    <div id="app">
        <input v-model="title"></input>
        <h1>{{title}}</h1>
        <button @click="startListen">开始监听</button>
        <button @click="stopListen">停止监听</button>
    </div>
</body>

</html>
<script>
    var app = new Vue({
        el: '#app',
        data: {
            title: 'hello',
            isListen: false,
            unWatch:null
        },
        methods: {
            startListen() {
                this.unWatch = this.$watch('title', (oldVal, newVal) => {
                    console.log(oldVal, newVal)
                });
            },
            stopListen(){
                this.unWatch();
            }
        }
    });
</script>