chromium/third_party/google-closure-library/closure/goog/demos/onlinehandler.html

<!DOCTYPE html>
<html>
<!--
Copyright The Closure Library Authors. All Rights Reserved.

Use of this source code is governed by the Apache License, Version 2.0.
See the COPYING file for details.
-->
<head>
<title>goog.net.OnlineHandler</title>
<script src="../base.js"></script>
<script>

goog.require('goog.events');
goog.require('goog.events.OnlineHandler');
goog.require('goog.net.NetworkStatusMonitor');

</script>
<style>

body {
  width: 30em;
  margin: 1em auto;
  text-align: justify;
  font: small sans-serif;
}

#out.online {
  border: 1px solid green;
  background: lightgreen;
}

#out.offline {
  border: 1px solid red;
  background: pink;
}

p {
  padding: 0.2em;
}

</style>
</head>
<body>

<p>This page reports whether your browser is online or offline. It will detect
changes to the reported state and fire events when this changes. The
OnlineHandler acts as a wrapper around the HTML5 events <code>online</code> and
<code>offline</code> and emulates these for older browsers.</p>

<p>Try changing <strong>File -> Work Offline</strong> in your browser.</p>

<p id=out></p>

<script>

var out = document.getElementById('out');
var oh = new goog.events.OnlineHandler;

function updateText() {
  out.innerHTML = 'Is online: ' + oh.isOnline();
  out.className = oh.isOnline() ? 'online' : 'offline';
}

goog.events.listen(oh, [goog.net.NetworkStatusMonitor.EventType.ONLINE,
                        goog.net.NetworkStatusMonitor.EventType.OFFLINE],
                   updateText);
goog.events.listen(window, 'unload', function() {
  oh.dispose();
});

updateText();

</script>
</body>
</html>