Edit in JSFiddle

new Vue({
el: '#app',
data: {
  message: 'Hello World!'
}
})
<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="utf-8">
  <title>Vue.js App</title>
</head>
<body>
<div id="app">
{{message}}
</div>
<script src="https://unpkg.com/vue"></script>
</body>
</html>
body{background-color:#f0f0e8;}
p{background-color:#65c59f}