Progressive Web Apps

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Dave Rupert / @davatron5000

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http://shoptalkshow.com

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http://godaytrip.com

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How many apps does the average mobile user download per month? Percent drop-off for each stage of your mobile app onboarding? Number of companies in the Top 10 app downloads according to COMSCORE? 0 20% 4

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Cats vs. Dogs, Right vs. Left, Pants vs. No pants

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We received a lot of feedback like “Where can I download it?” and “If it’s not on my homescreen I forget about it.”

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Requirement for an app that takes you deep into the woods, it must work deep in the woods.

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Alex Russell, Google TL;DR – “The future of the Web hangs on something I invented.”

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A background web worker with a few superpowers.

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LEAVE THE MAIN THREAD ALONE

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Offline

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“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.”

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Minimum Viable Product: An Offline Service Worker

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manifest.json offline.html service-worker.js (HTTPS too)

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manifest.json

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offline.html

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service-worker.js

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10x Faster Than React, Angular, Ember, and jQuery Combined!

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Install Activate Fetch Sync Push

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self.addEventListener(‘install’, function( event ) { event.waitUntil( // // Prime the caches // ) });

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“Hey event, wait until the stuff in these parenthesis are done before you tell the other events you fired.”

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self.addEventListener(‘activate’, function( event ) { event.waitUntil( // // Clear out old caches // ) });

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self.addEventListener(‘fetch’, function( event ) { event.respondWith( // // Instead of fetching stuff from the network, // try this stuff instead. // ) });

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“Hey (fetch) event, respond with this instead of what you were gonna do.”

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Quite literally one of the hardest problems in Computer Science. But at least we get to, you know, use JavaScript to do it.

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caches.open( cacheName ) caches.keys() caches.match( request ) caches.delete( key )

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~100 Lines of Fun, Stolen from adactio.com/serviceworker.js

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var staticCacheName = ‘static’; var version = ‘v1::’;

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function updateStaticCache() { return caches.open(version + staticCacheName) .then(function (cache) { return cache.addAll([ ‘/assets/application.css’ ‘/assets/application.js’, ‘/offline’ ]); }); };

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

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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); }) ); })); });

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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 });

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// 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; }

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// 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; }

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// 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; })

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// Step 2: Catch Stuff… .catch(function () { return caches.match(request).then(function (response) { return response || caches.match(‘/offline’); }) })

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// 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’ } }); } }); }) );

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The Last Step?

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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); }); }

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Browser Cache With Service Worker

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Multiple visits

2 minute session time

~5 minutes apart Depends on browser’s own heuristics.

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Asset pipelines, digest fingerprinting, and scope issues.

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function updateStaticCache() { return caches.open(version + staticCacheName) .then(function (cache) { return cache.addAll([ ‘<%= url_to_stylesheet “application” %>’ ‘<%= url_to_javascript “application” %>’, ‘/offline’ ]); }); };

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Nope Yep • assets/ • assets/ • serviceworker.js • logo.png • index.html • offline.html • manifest.json • logo.png • index.html • offline.html • manifest.json • serviceworker.js