Service Workers & Progressive Web Apps

What is the purpose of the 'activate' event in Service Workers?

self.addEventListener('activate', event => {
  event.waitUntil(
    Promise.all([
      caches.keys().then(cacheNames => {
        return Promise.all(
          cacheNames.map(cacheName => {
            if (!CURRENT_CACHES.includes(cacheName)) {
              return caches.delete(cacheName);
            }
          })
        );
      }),
      clients.claim()
    ])
  );
});

To start the Service Worker
To register the Service Worker
To clean up resources from old versions
The 'activate' event is crucial for: 1) Cleaning up resources (caches, indexedDB) from old Service Worker versions, 2) Migrating databases or updating cache structures, 3) Claiming clients with clients.claim(), 4) Preparing the Service Worker for handling fetch events. It's the ideal place for cleanup tasks that might disrupt still-running older versions.
To cache new resources

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