InstallEvent

The parameter passed into the oninstall handler, the InstallEvent interface represents an install action that is dispatched on the ServiceWorkerGlobalScope of a ServiceWorker. As a child of ExtendableEvent, it ensures that functional events such as FetchEvent are not dispatched during installation.

This interface inherits from the ExtendableEvent interface.

Constructor

InstallEvent.InstallEvent()

Creates a new InstallEvent object.

Properties

Inherits properties from its ancestor, Event.

InstallEvent.activeWorker Read only

Returns the ServiceWorker that is currently controlling the page.

Methods

Inherits methods from its parent, ExtendableEvent.

Examples

This code snippet is from the service worker prefetch sample (see prefetch running live.) The code calls ExtendableEvent.waitUntil() in ServiceWorkerGlobalScope.oninstall and delays 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 when any exception occurs.

The code snippet also shows a best practice for versioning caches used by the service worker. Although this example has only one cache, you can use this approach for multiple caches. The code maps a shorthand identifier for a cache to a specific, versioned cache name.

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) {
      return 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);
    })
  );
});

Browser compatibility

See also

• NotificationEvent
• Promise
• Fetch API