A recursive function to limit the number of items in a specified cache.

trimCache.js

// Limit the number of items in a specified cache.
function trimCache(cacheName, maxItems) {
  caches.open(cacheName)
  .then( cache => {
    cache.keys()
    .then(keys => {
      if (keys.length > maxItems) {
        cache.delete(keys[0])
        .then(
          trimCache(cacheName, maxItems)
        ); // end delete then
      } // end if
    }); // end keys then
  }); // end open then
} // end function