CODE EXAMPLE FOR JAVASCRIPT

communication with service worker

//one-way communication


// app.js - Somewhere in your web app
navigator.serviceWorker.controller.postMessage({
  type: 'MESSAGE_IDENTIFIER',
});
// service-worker.js
// On the Service Worker side we have to listen to the message event
self.addEventListener('message', (event) => {
  if (event.data && event.data.type === 'MESSAGE_IDENTIFIER') {
    // do something
  }
});

//two-way communication.


//Using the Broadcast API

// app.js
// Set up channel
const broadcast = new BroadcastChannel('count-channel');

// Listen to the response
broadcast.onmessage = (event) => {
  console.log(event.data.payload);
};

// Send first request
broadcast.postMessage({
  type: 'INCREASE_COUNT',
});

// service-worker.js
// Set up channel with same name as in app.js
const broadcast = new BroadcastChannel('count-channel');
broadcast.onmessage = (event) => {
  if (event.data && event.data.type === 'INCREASE_COUNT') {
    broadcast.postMessage({ payload: ++count });
  }
};

//Using the Client API

// app.js
// Listen to the response
navigator.serviceWorker.onmessage = (event) => {
  if (event.data && event.data.type === 'REPLY_COUNT_CLIENTS') {
    setCount(event.data.count);
  }
};

// Send first request
navigator.serviceWorker.controller.postMessage({
  type: 'INCREASE_COUNT_CLIENTS',
});

// service-worker.js
// Listen to the request
self.addEventListener('message', (event) => {
  if (event.data && event.data.type === 'INCREASE_COUNT') {
    // Select who we want to respond to
    self.clients.matchAll({
      includeUncontrolled: true,
      type: 'window',
    }).then((clients) => {
      if (clients && clients.length) {
        // Send a response - the clients
        // array is ordered by last focused
        clients[0].postMessage({
          type: 'REPLY_COUNT',
          count: ++count,
        });
      }
    });
  }
});