text: /**
   * Copyright 2015 Google Inc. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  /* eslint-env browser */
  'use strict'
  
  if ('serviceWorker' in navigator) {
    // Delay registration until after the page has loaded, to ensure that our
    // precaching requests don't degrade the first visit experience.
    // See https://developers.google.com/web/fundamentals/instant-and-offline/service-worker/registration
    window.addEventListener('load', function() {
      // Your service-worker.js *must* be located at the top-level directory relative to your site.
      // It won't be able to control pages unless it's located at the same level or higher than them.
      // *Don't* register service worker file in, e.g., a scripts/ sub-directory!
      // See https://github.com/slightlyoff/ServiceWorker/issues/468
      navigator.serviceWorker
        .register(`service-worker.js`, {
          scope: window.location.pathname
        })
        .then(function(reg) {
          // updatefound is fired if service-worker.js changes.
          reg.onupdatefound = function() {
            // The updatefound event implies that reg.installing is set; see
            // https://w3c.github.io/ServiceWorker/#service-worker-registration-updatefound-event
            var installingWorker = reg.installing
  
            installingWorker.onstatechange = function() {
              switch (installingWorker.state) {
                case 'installed':
                  if (navigator.serviceWorker.controller) {
                    // At this point, the old content will have been purged and the fresh content will
                    // have been added to the cache.
                    // It's the perfect time to display a "New content is available; please refresh."
                    // message in the page's interface.
                    console.log('New or updated content is available.')
                  } else {
                    // At this point, everything has been precached.
                    // It's the perfect time to display a "Content is cached for offline use." message.
                    console.log('Content is now available offline!')
                  }
                  break
  
                case 'redundant':
                  console.error('The installing service worker became redundant.')
                  break
              }
            }
          }
        })
        .catch(function(e) {
          console.error('Error during service worker registration:', e)
        })
    })
  }
  