CacheStorage.has()

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.

caches.has(cacheName).then(function(boolean) {
  // true: your cache exists!
});

cacheName

A DOMString 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(function(hasCache) {
  if (!hasCache) {
    someCacheSetupFunction();
  } else {
    caches.open('v1').then(function(cache) {
      return cache.addAll(myAssets);
    });
  }
}).catch(function() {
  // Handle exception here.
});

• Using Service Workers
• Cache
• WindowOrWorkerGlobalScope.caches