views/user.erb
<!doctype html>
<html lang="ja">
<head>
<meta charset="utf-8">
<title>OpenYo</title>
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
</head>
<body>
<h1>Send Yo to <%= @user %></h1>
<input type="submit" id="yo" value="Yo" /><br />
<input type="hidden" id="to" value="<%= @user %>" />
<span id="msgBox"></span><br />
<a href="/login/">Login</a>
</body>
<script src="/js/yo.js"></script>
</html>