The open() method of the CacheStorage interface returns a Promise that resolves to the Cache object matching the cacheName.
Note: If the specified Cache does not exist, a new cache is created with that cacheName and a Promise that resolves to this new Cache object is returned.
// "caches" is a global read-only variable, which is an instance of CacheStorage,
// For more info, refer to: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/caches
// Do something with your cache
If not, open the v1 cache using CacheStorage.open(), put the default network request in the cache using Cache.put() and return a clone of the default network request using return response.clone(). The last is necessary because put() consumes the response body.
If this fails (e.g., because the network is down), return a fallback response.