Untitled

 <html>
 <body>
   <div id="app">
     <p>{{msg}}</p>
     <button @click="sayHello">Hi!</button>
   </div>
   <script src="https://cdn.jsdelivr.net/npm/vue@2.5.16/dist/vue.js"></script>
   <script>
     new Vue({
       el: "#app",
       data: {
         msg: "Welcome"
       },
       methods: {
         sayHello(){
           this.msg = "Hello!"
         }
       },
       mounted(){
         //表示後にやりたいことはここに書ける
       }
     })
   </script>
 </body>
 </html>

// Code goes here

/* Styles go here */