Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Progressive Web Apps

Progressive Web Apps

A case-study talk on how we made DayTrip, an app that helps you leave your house on the weekends, into a minimum viable Progressive Web App with an offline service worker.

This talk was originally given at Austin JavaScript on a rainy, haunted night.

Dave Rupert

August 16, 2016
Tweet

More Decks by Dave Rupert

Other Decks in Programming

Transcript

  1. How many apps does the average mobile user download per

    month? 0 Percent drop-off for each stage of your mobile app onboarding? 20% Number of companies in the Top 10 app downloads according to COMSCORE? 4
  2. We received a lot of feedback like “Where can I

    download it?” and “If it’s not on my homescreen I forget about it.”
  3. Requirement for an app that takes you deep into the

    woods, it must work deep in the woods.
  4. “I don’t have bars, but if I did, they’d be

    full bars. Everyone knows I have great bars. Full bars. If I ever had less than full bars, I’d remember. But I don’t recall ever having less than full bars.”
  5. “Hey event, wait until the stuff in these parenthesis are

    done before you tell the other events you fired.”
  6. self.addEventListener(‘fetch’, function( event ) { event.respondWith( // // Instead of

    fetching stuff from the network, // try this stuff instead. // ) });
  7. Quite literally one of the hardest problems in Computer Science.

    But at least we get to, you know, use JavaScript to do it.
  8. function updateStaticCache() { return caches.open(version + staticCacheName) .then(function (cache) {

    return cache.addAll([ '/assets/application.css' '/assets/application.js', '/offline' ]); }); };
  9. 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    caches whose name is no longer valid return Promise.all( keys.filter(function (key) { return key.indexOf(version) !== 0; }) .map(function (key) { return caches.delete(key); }) ); })); });
  10. self.addEventListener('fetch', function (event) { // Step 1: Always fetch non-GET

    requests from the network // Step 2: For TEXT/HTML do this: // a) Try the network first // b) If that fails, fallback to the cache // c) If that doesn’t exist, show the offline page // Step 3: For non-TEXT/HTML (e.g. Images) do this: // a) Try the cache first // b) If that fails, try the network // c) If that fails, hijack the request });
  11. // Step 1: Always fetch non-GET requests from the network

    var request = event.request; if (request.method !== 'GET') { event.respondWith( fetch(request) .catch(function () { return caches.match('/offline'); }) ); return; }
  12. // Step 2 For TEXT/HTML do this… if (request.headers.get('Accept').indexOf('text/html') !==

    -1) { event.respondWith( fetch(request) // Then Stuff // Catch Stuff ); return; }
  13. // Step 2: Then Stuff… .then(function (response) { // Stash

    a copy of this page in the cache var copy = response.clone(); caches.open(version + staticCacheName) .then(function (cache) { cache.put(request, copy); }); return response; })
  14. // Step 2: Catch Stuff… .catch(function () { return caches.match(request).then(function

    (response) { return response || caches.match('/offline'); }) })
  15. // Step 3: For non-TEXT/HTML (e.g. Images) do this… event.respondWith(

    caches.match(request).then(function (response) { return response || fetch(request) .catch(function () { // If the request is for an image, show an offline placeholder if (request.headers.get('Accept').indexOf('image') !== -1) { return new Response('<svg>…</svg>', { headers: { 'Content-Type': 'image/svg+xml' } }); } }); }) );
  16. if ('serviceWorker' in navigator) { navigator.serviceWorker.register( '/service-worker.js', { scope: '/'

    }).then(function(reg) { console.log(‘Works! Scope is ' + reg.scope); }).catch(function(error) { console.log(‘Failed with ' + error); }); }
  17. - Multiple visits - > 2 minute session time -

    ~5 minutes apart Depends on browser’s own heuristics.
  18. function updateStaticCache() { return caches.open(version + staticCacheName) .then(function (cache) {

    return cache.addAll([ '<%= url_to_stylesheet "application" %>' '<%= url_to_javascript "application" %>', '/offline' ]); }); };
  19. Nope • assets/ • serviceworker.js • logo.png • index.html •

    offline.html • manifest.json Yep • assets/ • logo.png • index.html • offline.html • manifest.json • serviceworker.js
  20. • Fixes Scope Issues • Sets up route to Dynamic

    Service Worker in the root • Sets appropriate Expires headers