index.md

title	CacheStorage: keys() method
short-title	keys()
slug	Web/API/CacheStorage/keys
page-type	web-api-instance-method
browser-compat	api.CacheStorage.keys

{{APIRef("Service Workers API")}}{{SecureContext_Header}}{{AvailableInWorkers}}

The keys() method of the {{domxref("CacheStorage")}} interface returns a {{jsxref("Promise")}} that will resolve with an array containing strings corresponding to all of the named {{domxref("Cache")}} objects tracked by the {{domxref("CacheStorage")}} object in the order they were created. Use this method to iterate over a list of all {{domxref("Cache")}} objects.

You can access CacheStorage through the {{domxref("Window.caches")}} property in windows or through the {{domxref("WorkerGlobalScope.caches")}} property in workers.

Syntax

keys()

Parameters

None.

Return value

A {{jsxref("Promise")}} that resolves with an array of the {{domxref("Cache")}} names inside the {{domxref("CacheStorage")}} object.

Examples

In this code snippet we wait for an {{domxref("ServiceWorkerGlobalScope.activate_event", "activate")}} event, and then run a {{domxref("ExtendableEvent.waitUntil","waitUntil()")}} block that clears up any old, unused caches before a new service worker is activated. Here we have an allowlist containing the names of the caches we want to keep (cacheAllowlist). We return the keys of the caches in the {{domxref("CacheStorage")}} object using keys(), then check each key to see if it is in the allowlist. If not, we delete it using {{domxref("CacheStorage.delete()")}}.

this.addEventListener("activate", (event) => {
  const cacheAllowlist = ["v2"];

  event.waitUntil(
    caches.keys().then((keyList) =>
      Promise.all(
        keyList.map((key) => {
          if (!cacheAllowlist.includes(key)) {
            return caches.delete(key);
          }
          return undefined;
        }),
      ),
    ),
  );
});

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• Using Service Workers
• {{domxref("Cache")}}
• {{domxref("Window.caches")}} and {{domxref("WorkerGlobalScope.caches")}}