export.html

<!DOCTYPE html>
<html>
  <head>
    <title>Speadsheet export</title>
    <meta charset='utf-8' />
  </head>
  <body>
    <!--Add buttons to initiate auth sequence and sign out-->
    <button id="authorize-button" style="display: none;">Authorize</button>
    <button id="signout-button" style="display: none;">Sign Out</button>

    <pre id="content"></pre>

    <script type="text/javascript" src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
    <script src="https://www.gstatic.com/firebasejs/4.4.0/firebase.js"></script>
    <script src="js/firebase.js"></script>
    <script src="js/export.js"></script>

    <script async defer src="https://apis.google.com/js/api.js"
      onload="this.onload=function(){};handleClientLoad()"
      onreadystatechange="if (this.readyState === 'complete') this.onload()">
    </script>
  </body>
</html>