<!DOCTYPE html>
<!--
 | The onload event should fire on the window object when the document (and all
 | resource) have finished loading.
 |   https://www.w3.org/TR/html50/webappapis.html#event-handlers-on-elements,-document-objects,-and-window-objects
 -->
<html>
<head>
  <style>
    body {
      font-size: 60px;
    }
  </style>
</head>
<body>
  <script>
  window.addEventListener('load', function () {
    document.getElementById('text-box').innerHTML = "onLoad event fired.";
  })
  </script>

  <div id="text-box">
  </div>
</body>
</html>