この記事はまだボランティアによって 日本語 に翻訳されていません。ぜひ MDN に参加して翻訳を手伝ってください!
この記事を English (US) で読むこともできます。

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The ExtendableEvent interface extends the lifetime of the install and activate events dispatched on the global scope as part of the service worker lifecycle. This ensures that any functional events (like FetchEvent) are not dispatched until it upgrades database schemas and deletes the outdated cache entries.

If waitUntil() is called outside of the ExtendableEvent handler, the browser should throw an InvalidStateError; note also that multiple calls will stack up, and the resulting promises will be added to the list of extend lifetime promises.

Note: The behaviour described in the above paragraph was fixed in Firefox 43 (see bug 1189644.)

This interface inherits from the Event interface.

Note: This interface is only available when the global scope is a ServiceWorkerGlobalScope. It is not available when it is a Window, or the scope of another kind of worker.

Constructor

ExtendableEvent()
Creates a new ExtendableEvent object.

Properties

Doesn't implement any specific properties, but inherits properties from its parent, Event.

Methods

Inherits methods from its parent, Event.

ExtendableEvent.waitUntil()

Extends the lifetime of the event.  It is intended to be called in the install EventHandler for the installing worker and on the active EventHandler for the active worker.

Examples

This code snippet is from the service worker prefetch sample (see prefetch example live.) The code calls ExtendableEvent.waitUntil() in ServiceWorkerGlobalScope.oninstall, delaying treating the ServiceWorkerRegistration.installing worker as installed until the passed promise resolves successfully. The promise resolves when all resources have been fetched and cached, or else when any exception occurs.

The code snippet also shows a best practice for versioning caches used by the service worker. Though there's only one cache in this example, the same approach can be used for multiple caches. It maps a shorthand identifier for a cache to a specific, versioned cache name.

Note: In Chrome, logging statements are visible via the "Inspect" interface for the relevant service worker accessed via chrome://serviceworker-internals.

var CACHE_VERSION = 1;
var CURRENT_CACHES = {
  prefetch: 'prefetch-cache-v' + CACHE_VERSION
};

self.addEventListener('install', function(event) {
  var urlsToPrefetch = [
    './static/pre_fetched.txt',
    './static/pre_fetched.html',
    'https://www.chromium.org/_/rsrc/1302286216006/config/customLogo.gif'
  ];

  console.log('Handling install event. Resources to pre-fetch:', urlsToPrefetch);

  event.waitUntil(
    caches.open(CURRENT_CACHES['prefetch']).then(function(cache) {
      cache.addAll(urlsToPrefetch.map(function(urlToPrefetch) {
        return new Request(urlToPrefetch, {mode: 'no-cors'});
      })).then(function() {
        console.log('All resources have been fetched and cached.');
      });
    }).catch(function(error) {
      console.error('Pre-fetching failed:', error);
    })
  );
});
Important: When fetching resources, it's very important to use {mode: 'no-cors'} if there is any chance that the resources are served off of a server that doesn't support CORS. In this example, www.chromium.org doesn't support CORS.

Specifications

Specification Status Comment
Service Workers
The definition of 'ExtendableEvent' in that specification.
Working Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic support
Experimental
Chrome Full support 40Edge Full support 17Firefox Full support 44
Notes
Full support 44
Notes
Notes Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR).
IE No support NoOpera Full support 24Safari No support NoWebView Android Full support 40Chrome Android Full support 40Edge Mobile No support NoFirefox Android Full support 44Opera Android Full support 24Safari iOS No support NoSamsung Internet Android Full support 4.0
ExtendableEvent() constructor
Experimental
Chrome Full support 40Edge Full support 17Firefox Full support 44
Notes
Full support 44
Notes
Notes Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR).
IE No support NoOpera Full support 24Safari No support NoWebView Android Full support 40Chrome Android Full support 40Edge Mobile No support NoFirefox Android Full support 44Opera Android Full support 24Safari iOS No support NoSamsung Internet Android Full support 4.0
waitUntil
Experimental
Chrome Full support 40Edge Full support 17Firefox Full support 44IE No support NoOpera Full support 24Safari No support NoWebView Android Full support 40Chrome Android Full support 40Edge Mobile No support NoFirefox Android Full support 44Opera Android Full support 24Safari iOS No support NoSamsung Internet Android Full support 4.0

Legend

Full support  
Full support
No support  
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.

See also

ドキュメントのタグと貢献者

このページの貢献者: duduindo, fscholz, chrisdavidmills, jpmedley, teoli, Meggin
最終更新者: duduindo,