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Push API permite que as aplicações da Web recebam as mensagens submetidas para as mesmas a partir de um servidor, se a aplicação da Web está em primeiro plano, ou mesmo atualmente carregada, num agente de utilizador. Isto permite que os programadores entreguem notificações e atualizações assíncronas aos utilizadores que optem, resultando num melhor compromisso com os novos conteúdos atualizados.
Conceitos e utilziação de Push
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
ServiceWorkerGlobalScope.onpush event handler. This allows apps to react to push messages being received, for example, by displaying a notification (using
Each subscription is unique to a 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.
Activating a 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. Firefox allows a limited number (quota) of push messages to be sent to an application, although Push messages that generate notifications are exempt from this limit. The limit is refreshed each time the site is visited. In comparison, Chrome applies no limit, but requires that every push message causes a notification to be displayed.
Nota: As of Gecko 44, the allowed quota of push messages per application is not incremented when a new notification fires, when another is still visible, for a period of three seconds. This handles cases where a burst of notifications is received, and not all generate a visible notification.
Nota: Chrome versions earlier than 52 require you to set up a project on Google Cloud Messaging to send push messages, and use the associated project number and API key when sending push notifications. It also requires an app manifest, with some special parameters to use this service.
- Represents a push action, sent to the global scope of a
ServiceWorker. It contains information sent from an application to a
- Provides a way to receive notifications from third-party servers, as well as request URLs for push notifications. This interface has replaced the functionality offered by the obsolete
- Provides access to push data sent by a server, and includes methods to manipulate the received data.
- Provides a subcription's URL endpoint, and allows unsubscription from a push service.
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.
- Returns a reference to the
PushManagerinterface for managing push subscriptions including subscribing, getting an active subscription, and accessing push permission status. This is the entry point into using Push messaging.
- An event handler fired whenever a
pushevent occurs; that is, whenever a server push message is received.
- An event handler fired whenever a
pushsubscriptionchangeevent 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.)
Mozilla's ServiceWorker Cookbook contains many useful Push examples.
|Push API||Working Draft||Initial definition|
Compatibilidade de navegador
We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!
|Feature||Chrome||Firefox (Gecko)||Internet Explorer||Opera||Safari (WebKit)|
|Basic support||42.0||44.0 (44.0)||No support||?||?|
||No support||44.0 (44.0)||No support||No support||No support|
|Feature||Android||Android Webview||Firefox Mobile (Gecko)||Firefox OS||IE Mobile||Opera Mobile||Safari Mobile||Chrome for Android|
|Basic support||No support||No support||48.0 (48.0)||No support||?||?||?||42.0|
||No support||No support||48.0 (48.0)||No support||No support||No support||No support||No support|
-  Currently available only on desktop versions of Firefox; also, push messages are only delivered when Firefox is running.
-  This is currently not implemented. See the Microsoft Edge status information.
-  Push (and Service Workers) have been disabled in the Firefox 45 and 52 Extended Support Releases (ESR.)
-  Push has been enabled by default on Firefox for Android version 48.