<html> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> </head> <body> <ul id="statuses"></ul> <script type="text/javascript"> const list = document.getElementById("statuses"); function appendOnlineStatus(onLine) { const label = onLine ? "device is now online" : "device is now offline"; const txt = document.createTextNode(label); const li = document.createElement("li"); li.appendChild(txt); list.appendChild(li); } window.addEventListener('offline', () => appendOnlineStatus(false)); window.addEventListener('online', () => appendOnlineStatus(true)); appendOnlineStatus(navigator.onLine); </script> </body> </html>