iframe_sync_xhr_unload.html

Enable keyboard shortcuts

<!DOCTYPE HTML>

<html>

<body>

  <script type="application/javascript">

function o() {

 var xhr = new XMLHttpRequest();

 xhr.open("GET", "sync_xhr_unload.sjs", false);

 try { xhr.send(); } catch(e) {}

window.addEventListener("beforeunload", o);

window.addEventListener("unload", o)

  </script>

</body>

</html>