<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>下拉框</title>
</head>
<body>
    <div id="app">
        <p>请选择语言，已选择{{languages.length}}种</p>
        <select name="s1" id="s1" v-model="languages" multiple>
            <option value="python">python</option>
            <option value="javascript">javascript</option>
            <option value="php">php</option>
        </select>
    </div>

    <script src="../js/vue.js"></script>

    <script>
        let vm = new Vue({
            el:'#app',
            data:{
                languages:[]
            }
        });
    </script>
</body>
</html>