How to alert the user when there's no internet connection

Question

I need to alert the user with the following conditions;

1. Request timed out
2. No internet connection
3. Unable to reach the server

He

Answer 1

Exactly as Simon said, you can use

document.addEventListener("offline", youCallbackFn, false);

or you can interrogate the boolean property

navigator.onLine

(Should return true or false)

However, this technique will tell you whether device is connected. The caveat is such that device can be connected to WiFi, but the router might be offline. In that case, use a polling mechanism, like timely Ext.Ajax.request with lower timeouts. Timeout expired = offline.