index.html

<!DOCTYPE html>
<html lang="en">
    <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="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
    </head>
    <body>
        <div id="app-5">
            <p>{{message}}</p>
            <button v-on:click="reverseMessage()">反转消息</button>
        </div>
    </body>

    <script>
        var app5 = new Vue({
            el: "#app-5",
            data: {
                message: "Hello Vue.js!",
            },
            methods: {
                reverseMessage: function () {
                    this.message = this.message.split("").reverse().join("");
                },
            },
        });
    </script>
</html>