[PWA] Add Push Notifications to a PWA with React in Chrome and on Android

On Android and in Chrome (but not on iOS), it's possible to send push notifications with a PWA. We'll start by asking the user for permission to send them push notifications, and then look at how to intercept the push event in a service worker. We can test the push notifications directly in Chrome's devtools, and we will also make a button that can trigger a push notification directly from the PWA app code itself.

Install:

npm install web-push -g

Generate the key:

web-push generate-vapid-keys

In src/serviceworker.js (Generated by create-react-app) we need to save access to the service worker registration here. Set global.registration = registration.

function registerValidSW(swUrl, config) {
  navigator.serviceWorker
    .register(swUrl)
    .then(registration => {

      global.registration = registration

    ...
    })
    .catch(error => {
      console.error('Error during service worker registration:', error);
  });
}

Register function for push notification:

  function subscribe () {
    const key = 'xxx-xxx-xxx';
    global.registration.pushManager.subscribe({
      userVisibleOnly: true,
      applicationServerKey: urlB64ToUint8Array(key)
      }).then(sub => {
        console.log("Subscribed!")
      }).catch(err => {
        console.log("Did not subscribe.")
      })
  }

function urlB64ToUint8Array(base64String) {
  const padding = '='.repeat((4 - base64String.length % 4) % 4);
  const base64 = (base64String + padding)
    .replace(/\-/g, '+')
    .replace(/_/g, '/');

  const rawData = window.atob(base64);
  const outputArray = new Uint8Array(rawData.length);

  for (let i = 0; i < rawData.length; ++i) {
    outputArray[i] = rawData.charCodeAt(i);
  }
  return outputArray;
}

Now in src/sw.js: we can listen for a 'push', event from the push server just like we did for fetch. Add a push eventListener. We're going to tell the event to waitUntil we show a push notification. Access the server worker registration with self.registration and call showNotification. That takes the title as the first argument and a hash of options as the second. For now, we'll set the iconto an icon that we already have in the public folder and the body to whatever text comes through the push from the server.

self.addEventListener('push', event => {
  event.waitUntil(self.registration.showNotification('Todo List', {
    icon: '/icon-120.jpg',
    body: event.data.text()
  }))
})

Last, in App.js, we write code to send push message:

  testPushMessage = () => {
    global.registration.showNotification('Test Message', {
      body: 'Success!'
    })
  }