CacheStorage 缓存存储

The CacheStorage interface represents the storage for Cache objects. It provides a master directory of all the named caches that a ServiceWorker, other type of worker or window scope can access (you don't have to use it with service workers, even though that is the spec that defines it) and maintains a mapping of string names to corresponding Cache objects.

CacheStorage also exposes CacheStorage.open() and CacheStorage.match(). Use CacheStorage.open() to obtain a Cache instance. Use CacheStorage.match() to check if a given Request is a key in any of the Cache objects that the CacheStorage object tracks.

You can access CacheStorage through the global caches property.

方法

CacheStorage.match()

Checks if a given Request is a key in any of the Cache objects that the CacheStorage object tracks and returns a Promise that resolves to that match.

CacheStorage.has()

Returns a Promise that resolves to true if a Cache object matching the cacheName exists.

CacheStorage.open()

Returns a Promise that resolves to the Cache object matching the cacheName (a new cache is created if it doesn't exist.)

CacheStorage.delete()

Finds the Cache object matching the cacheName, and if found, deletes the Cache object and returns a Promise that resolves to true. If no Cache object is found, it returns false.

CacheStorage.keys()

Returns a Promise that will resolve with an array containing strings corresponding to all of the named Cache objects tracked by the CacheStorage. Use this method to iterate over a list of all the Cache objects.

举例

This code snippet is from the MDN sw-test example (see sw-test running live.) This service worker script waits for an InstallEvent to fire, then runs waitUntil to handle the install process for the app. This consists of calling CacheStorage.open to create a new cache, then using Cache.addAll to add a series of assets to it.

In the second code block, we wait for a FetchEvent to fire. We construct a custom response like so:

1. Check whether a match for the request is found in the CacheStorage. If so, serve that.
2. If not, fetch the request from the network, then also open the cache created in the first block and add a clone of the request to it using Cache.put (cache.put(event.request, response.clone()).)
3. If this fails (e.g. because the network is down), return a fallback response.

Finally, return whatever the custom response ended up being equal to, using FetchEvent.respondWith.

this.addEventListener('install', function(event) {
  event.waitUntil(
    caches.open('v1').then(function(cache) {
      return cache.addAll([
        '/sw-test/',
        '/sw-test/index.html',
        '/sw-test/style.css',
        '/sw-test/app.js',
        '/sw-test/image-list.js',
        '/sw-test/star-wars-logo.jpg',
        '/sw-test/gallery/bountyHunters.jpg',
        '/sw-test/gallery/myLittleVader.jpg',
        '/sw-test/gallery/snowTroopers.jpg'
      ]);
    })
  );
});
this.addEventListener('fetch', function(event) {
  var response;
  event.respondWith(caches.match(event.request).catch(function() {
    return fetch(event.request);
  }).then(function(r) {
    response = r;
    caches.open('v1').then(function(cache) {
      cache.put(event.request, response);
    });
    return response.clone();
  }).catch(function() {
    return caches.match('/sw-test/gallery/myLittleVader.jpg');
  }));
});

说明

浏览器兼容性

[1] Service workers (and Push) have been disabled in the Firefox 45 Extended Support Release (ESR.)

查看其他

• Using Service Workers
• Cache
• WorkerGlobalScope.caches