5

I currently learning about service workers, and in particular subscribing a user to push notifications. I've worked through the Web Push Notifications Guide and Adding Push Notifications to a Web App Code Lab that Google publishes - but I'm seeing two different ways of asking for a user's permission.

The guide asks using the Notification interface of the Notifications API like this and then calls subscribe() based on the return value of .requestPermission():

function askPermission() {
  return new Promise(function(resolve, reject) {
    const permissionResult = Notification.requestPermission(function(result) {
      resolve(result);
    });

    if (permissionResult) {
      permissionResult.then(resolve, reject);
    }
  })
  .then(function(permissionResult) {
    if (permissionResult !== 'granted') {
      throw new Error('We weren\'t granted permission.');
    }
  });
}

And the Code Lab asks by only calling .subscribe() (which will bring up the notification prompt) directly on the service worker registration's PushManager like this:

function subscribeUser() {
  const applicationServerKey = urlB64ToUint8Array(applicationServerPublicKey);
  swRegistration.pushManager.subscribe({
    userVisibleOnly: true,
    applicationServerKey: applicationServerKey
  })
  .then(function(subscription) {
    console.log('User is subscribed.');

    updateSubscriptionOnServer(subscription);

    isSubscribed = true;

    updateBtn();
  })
  .catch(function(err) {
    console.log('Failed to subscribe the user: ', err);
    updateBtn();
  });
}

I've looked through the mozilla docs for PushManager.subscribe() and Notification.requestPermission() but am struggling to identify the trade-offs of each of Google's flows and in particular whether or not the extra step of Notification.requestPermission(..) is necessary.

It's worth noting that .subscribe() is currently marked as an experimental feature where-as .requestPermission() is not.

Vadim Kotov
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Kevbot
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1 Answers1

6

As with most times I end up posting on Stack Overflow, I found the answer by re-looking through everything. In fact, the Guide I referenced above answers this question directly:

There is one side effect of calling subscribe(). If your web app doesn't have permissions for showing notifications at the time of calling subscribe(), the browser will request the permissions for you. This is useful if your UI works with this flow, but if you want more control (and I think most developers will), stick to the Notification.requestPermission() API that we used earlier.

Kevbot
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