When you have two levels of connectivity detection, browser online and offline — which is typically physical media connectivity or in-browser online/offline mode — and network online and offline — which is the actual access online to your web server — you can begin modifying your web application to react properly to both groups of online and offline events:

addEventListener('online', function(){
   // The browser has come online.
 }, false);
 addEventListener('offline', function(){
   // The browser has gone offline.
 }, false);
 addEventListener('netonline', function(){
   // The network has come online.
}, false);
 addEventListener('netoffline', function(){
   // The network has gone offline.
}, false);

Considering that ...

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