<!doctype html>
<title>Event loop pause for beforeunload</title>
<script>
var counter = 0;

onload = function count() {
  document.getElementById("log").textContent = counter++
  setTimeout(count, 200);
}

addEventListener("beforeunload",
function(e) {
  e.preventDefault()
},
false);
</script>
<ul>
<li>Click on the link below. When the prompt appears the counter at the bottom must stop incrementing.
<li>Opt not to leave the page. The counter must start incrementing again
</ul>
<p><a href="">Click here</a>
<div id="log"></div>