index.js

workbox.routing.registerRoute(/\.(?:png|gif|jpg|jpeg|svg)$/,
 workbox.strategies.cacheFirst({
   cacheName: 'images',
   plugins: [
     new workbox.expiration.Plugin({
       maxEntries: 60,
       maxAgeSeconds: 30 * 24 * 60 * 60, // 30 Days
     }),
   ],
 }),
);