Hello.erb

<template>
  <p>Hello, {%= @user.name %}!</p>
  <div id="replace-me"></div>
</template>

<script>
document.getElementById("replace-me").innerHTML = "Welcome to the future.";
</script>

<style scoped>
p {
  font-size: 2em;
  text-align: center;
}
</style>