HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>stop polling</title>
</head>
<body>
  <p>Switch tabs to stop/resume polling.</p>
  <pre id="out">Starting poll...</pre>
  <script>
    var out = document.getElementById("out");
    var timerId = setInterval(function () {
      out.textContent += "\npoll";
    }, 2000);
    document.addEventListener("visibilitychange", function () {
      if (document.hidden) {
        clearInterval(timerId);
        timerId = null;
        out.textContent += "\npolling stopped";
      } else if (!timerId) {
        timerId = setInterval(function () {
          out.textContent += "\npoll";
        }, 2000);
        out.textContent += "\npolling resumed";
      }
    });
  </script>
</body>
</html>

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