<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<input type="text" id="input" />
<script src="https://unpkg.com/vue@2.1.3/dist/vue.js"></script>
<script>
let data = {
message: "Hello world",
};
document.querySelector('#input').value = data.message;
</script>
</body>
</html>