Setting the email address based on a query string

page.htm

<script>
document.addEventListener("DOMContentLoaded", () => { 
  const url = new URL(window.location)
  const email = url.searchParams.get("email_address")
  if (email) {
  document.querySelectorAll("input[type='email']").forEach((el) => el.value = email);
  } 
});
</script>