serviceWorker.js

const staticCacheName = 'ecolyo-v1'
const urlsToCache = ['index.html', 'offline.html']

// Install SW
self.addEventListener('install', event => {
  event.waitUntil(
    caches.open(staticCacheName).then(cache => {
      return cache.addAll(urlsToCache)
    })
  )
})

// Listen for requests
self.addEventListener('fetch', event => {
  event.respondWith(
    caches.match(event.request).then(() => {
      return fetch(event.request).catch(() => caches.match('offline.html'))
    })
  )
})

// Activate the SW
self.addEventListener('activate', event => {
  const cacheWhitelist = []
  cacheWhitelist.push(staticCacheName)

  event.waitUntil(
    caches.keys().then(cacheNames =>
      Promise.all(
        cacheNames.map(cacheName => {
          if (!cacheWhitelist.includes(cacheName)) {
            return caches.delete(cacheName)
          }
        })
      )
    )
  )
})