Push API
I want to read about the Push API because I want to add push notifications to this site.
References
Notes
The Push API gives web applications the ability to receive messages pushed to them from a server, whether or not the web app is in the foreground, or even currently loaded, on a user agent. This lets developers deliver asynchronous notifications and updates to users that opt in, resulting in better engagement with timely new content.
For an app to receive push notifications, it has to have an active service worker. When the service worker is active, it can subscribe to push notifications, using PushManager.subscribe().
The resulting PushSubscription includes all the information that the application needs to send a push message: an endpoint and the encryption key needed for sending data.
The service worker will be started as necessary to handle incoming push messages, which are delivered to the onpush event handler. This allows apps to react to push messages being received, for example, by displaying a notification (using ServiceWorkerRegistration.showNotification()).
Each subscription is unique to the service worker. The endpoint for the subscription is a unique capability URL: knowledge of the endpoint is all that is necessary to send a message to your application. The endpoint URL therefore needs to be kept secret, or other applications might be able to send push messages to your application.
Capability URLs grant access to a resource to anyone who has the URL. There are times when this is useful, for example one-shot password reset URLs, but overuse can be problematic as URLs cannot generally be kept secret. This document provides some good practices for web developers who wish to incorporate capability URLs into their applications.
W3C Docs
Activating s service worker to deliver a push message can result in increased resource usage, particularly of the battery. Different browsers have different schemes for handling this, there is currently no standard mechanism.
Some basic questions you can answer to determine if a push notification is needed:
- Is there someone waiting in real-time for a response?
- Is up-to-the-minute updating necessary?
- Is there breaking news that is timely?
Interfaces
PushEvent
Represents a push action, sent the global scope of a ServiceWorker. It contains information sent from an application to a PushSubscription.
PushManager
Provides a way to receive notifications from third-party servers, as well as request URLs for push notifications.
PushMessageData
Provides access to push data sent by a server, and includes methods to manipulate the received data.
PushSubscription
Provides a subscription URL endpoint, and allows unsubscribing from a push service.
PushSubscriptionOptions
Represents the options associated with the push subscription.
Service Worker Additions
The following additions to the Service Worker API have been specified in the Push API spec to provide an entry point for using push messages. They also monitor and respond to push and subscription change events.
ServiceWorkerRegistration.pushManager
Returns a reference to the PushManager interface for managing push subscriptions including subscribing, getting an active subscription, and accessing push permission status. This is the entry point into using Push messaging.
onpush
An event handler hired whenever a push event occurs; that is, whenever a server push message is received.
onsubscriptionchange
An event handler fired whenever a pushsubscriptionchange event occurs; for example, when a push subscription has been invalidated, or is about to be invalidated (e.g. when a push service sets an expiration time).
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