sw.js

---
layout: null
---
// Based on ServiceWorker from sessionize.com
(function () {
  'use strict';

  var version = 'CacheId-{% css_version %}::NetworkFirst';
  var offlineUrl = '/offline/';

  // Store core files in a cache (including a page to display when offline)
  function updateStaticCache() {
    return caches.open(version)
      .then(function (cache) {
        return cache.addAll([
          offlineUrl,
          '/','/css/site.css'
        ]);
      });
  }

  function addToCache(request, response) {
    if (!response.ok)
      return;

    var copy = response.clone();
    caches.open(version)
      .then(function (cache) {
        cache.put(request, copy);
      });
  }

  self.addEventListener('install', function (event) {
    event.waitUntil(updateStaticCache());
  });

  self.addEventListener('activate', function (event) {
    event.waitUntil(
      caches.keys()
      .then(function (keys) {
        // Remove caches whose name is no longer valid
        return Promise.all(keys
          .filter(function (key) {
            return key.indexOf(version) !== 0;
          })
          .map(function (key) {
            return caches.delete(key);
          })
        );
      })
    );
  });

  self.addEventListener('fetch', function (event) {
    var request = event.request;

    // Always fetch non-GET requests from the network
    if (request.method !== 'GET') {
      event.respondWith(
        fetch(request)
        .catch(function () {
          return caches.match(offlineUrl);
        })
      );
      return;
    }

    event.respondWith(
      fetch(request)
      .then(function (response) {
        // Stash a copy of this page in the cache
        addToCache(request, response);
        return response;
      })
      .catch(function () {
        return caches.match(request)
          .then(function (response) {
            return response || caches.match(offlineUrl);
          })
          .catch(function () {
            if (request.headers.get('Accept').indexOf('image') !== -1) {
              return new Response('<svg role="img" aria-labelledby="offline-title" viewBox="0 0 400 300" xmlns="http://www.w3.org/2000/svg"><title id="offline-title">Offline</title><g fill="none" fill-rule="evenodd"><path fill="#D8D8D8" d="M0 0h400v300H0z"/><text fill="#9B9B9B" font-family="Helvetica Neue,Arial,Helvetica,sans-serif" font-size="72" font-weight="bold"><tspan x="93" y="172">offline</tspan></text></g></svg>', { headers: { 'Content-Type': 'image/svg+xml' } });
            }
          });
      })
    );

  });

})();