main.js

(function () {
  //If serviceWorker supports, then register it.
  if ("serviceWorker" in navigator) {
    navigator.serviceWorker.register('./serviceWorker.js', { scope: "./" }) //setting scope of sw
    .then(function(registration) {
      console.info('Service worker is registered!');
      checkForPageUpdate(registration); // To check if new content is updated or not
    })
    .catch(function(error) {
      console.error('Service worker failed ', error);
    });
  }

  // To content update on service worker state change
  function checkForPageUpdate(registration) {
    // onupdatefound will fire on first time install and when serviceWorker.js file changes      
    registration.addEventListener("updatefound", function() {
      // To check if service worker is already installed and controlling the page or not
      if (navigator.serviceWorker.controller) {
        var installingSW = registration.installing;
        installingSW.onstatechange = function() {
          console.info("Service Worker State :", installingSW.state);
          switch(installingSW.state) {
            case 'installed':
              // Now new contents will be added to cache and old contents will be remove so
              // this is perfect time to show user that page content is updated.
              toast('Site is updated. Refresh the page.', 5000);
              break;
            case 'redundant':
              throw new Error('The installing service worker became redundant.');
          }
        }
      }
    });
  }
})();

/**
self.addEventListener('install',function(e){
    e.waitUntil(
        Promise.all([caches.open(STATIC_CACHE_NAME),caches.open(APP_CACHE_NAME),self.skipWaiting()]).then(function(storage){
            var static_cache = storage[0];
            var app_cache = storage[1];
            return Promise.all([static_cache.addAll(CACHE_STATIC),app_cache.addAll(CACHE_APP)]);
        })
    );
});

self.addEventListener('activate', function(e) {
    e.waitUntil(
        Promise.all([
            self.clients.claim(),
            caches.keys().then(function(cacheNames) {
                return Promise.all(
                    cacheNames.map(function(cacheName) {
                        if (cacheName !== APP_CACHE_NAME && cacheName !== STATIC_CACHE_NAME) {
                            console.log('deleting',cacheName);
                            return caches.delete(cacheName);
                        }
                    })
                );
            })
        ])
    );
});**/