The has() method of the CacheStorage interface returns a Promise that resolves to true if a Cache object matches the cacheName.

You can access CacheStorage through the global caches property.

cacheName

A string representing the name of the Cache object you are looking for in the CacheStorage.

a Promise that resolves to true if the cache exists or false if not.

The following example first checks whether a cache called 'v1' exists. If so, we add a list of assets to it. If not then we run some kind of cache set-up function.

caches
  .has("v1")
  .then((hasCache) => {
    if (!hasCache) {
      someCacheSetupFunction();
    } else {
      caches.open("v1").then((cache) => cache.addAll(myAssets));
    }
  })
  .catch(() => {
    // Handle exception here.
  });

• Using Service Workers
• Cache
• caches