f7-v5-connection.js

const app = new Framework7(/*...*/);

if (app.online) {
  console.log('online!');
}
if (!app.online) {
  console.log('offline!');
}

app.on('online', () => {
  console.log('connection established')
});
app.on('offline', () => {
  console.log('lost connection')
});
// or with single event
app.on('connection', (isOnline) => {
  if (isOnline) {
    console.log('connection established')
  } else {
    console.log('lost connection')
  }
});