Print service worker cache sizes and overall bytes cached.

sw_caching_size.js

/**
 * @author ebidel@ (Eric Bidelman)
 * License Apache-2.0
 */
 
// Prints the bytes cached by service worker. Breaks out each cache
// overall in-memory bytes used by the Cache Storage API for the site.
 
async function getCacheStoragesAssetTotalSize() {
  // Note: opaque (i.e. cross-domain, without CORS) responses in the cache will return a size of 0.
  const cacheNames = await caches.keys();

  let total = 0;

  const sizePromises = cacheNames.map(async cacheName => {
    const cache = await caches.open(cacheName);
    const keys = await cache.keys();
    let cacheSize = 0;

    await Promise.all(keys.map(async key => {
      const response = await cache.match(key);
      const blob = await response.blob();
      total += blob.size;
      cacheSize += blob.size;
    }));

    console.log(`Cache ${cacheName}: ${cacheSize} bytes`);
  });

  await Promise.all(sizePromises);

  return `Total Cache Storage: ${total} bytes`;
}