sw-toolbox – A Collection of Tools for Service Workers

Service Worker Toolbox provides some simple helpers for use in creating your own service workers. Specifically, it provides common caching strategies for dynamic content, such as API calls, third-party resources, and large or infrequently used local resources that you don’t want precached.

The code itself is very readable I must say:

importScripts('sw-toolbox.js');

toolbox.precache([
  '/css/app.css',
  '/img/logo.png'
]);

toolbox.router.get('/css*', toolbox.cacheFirst);
toolbox.router.get('/img*', toolbox.cacheFirst);
toolbox.router.get('/(.*)', toolbox.networkFirst, { networkTimeoutSeconds: 5});

A bit more advanced is to precache a “you’re offline” page first, and return that in case a user is offline (src):

importScripts('sw-toolbox.js');

toolbox.precache([
  '/offline',
  '/img/offline.png',
   // …
]);

// …

toolbox.router.get('/(.*)', function(request, values, options) {
  // networkFirst will attempt to return a response from the network,
  // then attempt to return a response from the cache.
  return toolbox.networkFirst(request, values, options).catch(function(error) {
    // If both the network and the cache fail, then `.catch()` will be triggered,
    // and we get a chance to respond with our cached fallback page.
    if (request.method === 'GET' && request.headers.get('accept').includes('text/html')) {
      return toolbox.cacheOnly(new Request('/offline'), values, options);
    }
    throw error;
  });
});

sw-toolbox →
sw-toolbox (GitHub) →