【vue】watchEffect 自动侦听器

watchEffect：自动监听值的变化

• 获取旧值时，不是很方便，建议用watch

<!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">
        爱好
        <select v-model="hobby">
            <option value="">请选择</option>
            <option value="reading">阅读</option>
            <option value="swimming">游泳</option>
            <option value="running">跑步</option>
        </select>
        <hr>
        年
        <select v-model="date.year">
            <option value="">请选择</option>
            <option value="2021">2021</option>
            <option value="2022">2022</option>
            <option value="2023">2023</option>
            <option value="2024">2024</option>
        </select>

        月
        <select v-model="date.month">
            <option value="">请选择</option>
            <option value="1">1</option>
            <option value="2">2</option>
            <option value="3">3</option>
            <option value="4">4</option>
            <option value="5">5</option>
            <option value="6">6</option>
            <option value="7">7</option>
            <option value="8">8</option>
            <option value="9">9</option>
            <option value="10">10</option>
            <option value="11">11</option>
            <option value="12">12</option>
        </select>

    </div>

    <script type="module">
        import { createApp, reactive, ref, watchEffect } from './vue.esm-browser.js'
        createApp({
            setup() {
                const hobby = ref("")
                const date = reactive({
                    year: "",
                    month: ""
                })
                //自动监听
                watchEffect(() => {
                    console.log("----- 自动监听开始")
                    console.log(hobby.value)
                    console.log(date.year, date.month)
                    console.log("自动监听结束 -----")
                })

                return {
                    date,
                    hobby
                }
            }
        }).mount("#app")
    </script>
</body>

</html>

参考

https://www.bilibili.com/video/BV1nV411Q7RX