PWA Day06 - generic fallback(network error)

sw.js

self.addEventListener('fetch', function(event) {
  event.respondWith(
    // Try the cache
    caches
      .match(event.request)
      .then(function(response) {
        if (response) {
          return response
        }
        return fetch(event.request)
          .then(function(response) {
            if (response.status === 404) {
              return caches.match('pages/404.html')
            }
            return response
          })
      })
      .catch(function() {
        // If both fail, show a generic fallback:
        return caches.match('/offline.html')
      })
  )
})