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Velocity EU 2014 — Offline-first web apps
- 1. Offline-first web apps Matt Andrews, Financial Times @andrewsmatt, mattandre.ws
- 4. • HTML5 • Offline-first • Sideways-swipe-enabled • Add-to-home-screen-able • iOS • Web App
- 5. • HTML5 • Offline-first • Sideways-swipe-enabled • Add-to-home-screen-able • iOS • Android • Web App
- 6. • HTML5 • Offline-first • Sideways-swipe-enabled • Add-to-home-screen-able • iOS • Android • Windows • Web App
- 7. • HTML5 • Offline-first • Sideways-swipe-enabled • Add-to-home-screen-able • iOS • Android • Windows • Firefox • Web App
- 8. • HTML5 • Offline-first • Sideways-swipe-enabled • Add-to-home-screen-able • iOS • Android • Windows • Firefox • ALL THE THINGS • Web App
- 9. What’s so important about offline?
- 13. Internet Connections • Not just on or off • On can sometimes mean off • Slow can be worse than off
- 15. So why is FT app so slow?
- 16. AppCache CACHE MANIFEST /my-font.ttf /my-styles.css ! ! <DOCTYPE html> <html manifest="mywebapp.manifest">
- 17. AppCache CACHE MANIFEST /my-font.ttf /my-styles.css ! NETWORK: * <DOCTYPE html> <html manifest="mywebapp.manifest">
- 18. AppCache Hacks • Varying the response of every page based on whether a cookie is set (hack needs to be added to our CDN as well as back end) • Returning an HTTP error on the manifest request when that cookie is not set; • Created an iframe to load a page that loads the manifest rather than referencing it directly. • Without the NETWORK: * hack in your AppCache manifest you will break all non-offline'd resources. • Putting all our API methods on a path starting with /api so that our FALLBACK doesn’t interfere with ajax requests. • Returning different Cache-Control headers on Internet Explorer 10+.
- 19. @andrewsmatt
- 21. Service Workers + Fetch + Caches
- 22. Fetch API XMLHttpRequest revamped
- 23. var xhr = new XMLHttpRequest(); xhr.onreadystatechange = function() { if (xhr.readyState === 4) { if (xhr.status === 200) { alert(xhr.responseText); } else { alert('There was a problem.'); } } }; xhr.ontimeout = function() { alert('There was a problem.'); }; xhr.open('GET', 'http://a.b/c.html'); with XMLHttpRequest
- 24. fetch('http://a.b/c.html') .then(function(response) { return response.text(); // can be .json, .blob }) .then(function(text) { alert(text); }) .catch(function() { alert('There was a problem.'); }); with Fetch API
- 25. Using Fetch Native within Service Workers only Browser-only polyfill:- github.com/github/fetch ‘Isomorphic’ Fetch Polyfill that works in Node and in the browser via Browserify:- bit.ly/iso-fetch
- 26. Cache API Caching that speaks JavaScript
- 27. caches.open(‘my-app’) .then(function(cache) { return cache .addAll([ ‘/my-styles.css’, ‘/my-font.ttf’ ]); }); Pre-Cache URLs
- 28. caches.match(new Request(‘/my-styles.css’)) .then(function(response) { // got back /my-styles.css }); ‘Fetch’ URLs from Cache
- 29. caches.open(‘my-app’) .then(function(cache) { return cache.put(‘/my-fake-endpoint’, new Response(‘Hello!’)); }); Put ‘fake’ responses into the Cache
- 30. Put ‘fake’ responses into the Cache WARNING: the difference between ‘add’ & ’put’ is different to the difference between IndexedDB’s ‘add’ & ‘put’ add put IndexedDB INSERT INSERT OR UPDATE Service Worker Caches INSERT OR UPDATE INSERT OR UPDATE
- 31. caches.open(‘my-app’) .then(function(cache) { return cache.keys(); }) .then(function(keys) { return cache.addAll(keys); }); Update content in the Cache WARNING: This will ‘break’ any ‘fake requests’ that have been ‘put’ted WARNING: The Service Worker Cache is in addition to the regular HTTP Cache.
- 32. Service Workers
- 33. <DOCTYPE html> <html> <head><title>mattandre.ws</title></head> <body> <h1>My offline website</h1> <script> navigator.serviceWorker.register(‘./sw.js’) </script> </body> </html>
- 34. sw.js:- this.oninstall = function(event) { // prepare website to work offline, // e.g. cache resources }; this.onfetch = function(event) { // listen to, manipulate and/or respond // requests from your app };
- 36. sw.js:- this.oninstall = function(event) { var promise = caches.open(‘my-app’) .then(function(cache) { return cache .addAll([ ‘/my-styles.css’, ‘/my-font.ttf’ ]); }); ! event.waitUntil(promise); };
- 37. <DOCTYPE html> <html> <head><title>mattandre.ws</title></head> <body> <h1>My offline website</h1> <script> navigator.serviceWorker.register(‘./sw.js’) .then(function() { // installed }) .catch(function() { // didn’t install :( }); </script> </body> </html>
- 38. sw.js:- this.onfetch = function(event) { var promise; promise = caches.match(event.request) .catch(function() { return fetch(event.request); }); event.respondWith(promise); };
- 42. No Caches The Service Worker Cache API does not work yet but a Polyfill exists that uses IndexedDB underneath:- bit.ly/caches-polyfill
- 43. Storage Limits • Every origin (protocol+domain+port) gets an allowance of offline storage, typically 50mb • Allowance shared between IndexedDB & Service Workers • Each origin only has access to data in its caches & databases.
- 44. Some JavaScript APIs are not available in Service Worker:- • LocalStorage • Synchronous ajax
- 45. https
- 46. You can use Service Workers to make offline-first websites… …or just to make normal websites faster.
- 48. Advanced Offline • Simple Caches not always enough • Use IndexedDB for more structured data, e.g. user preferences, bookmarks • Don’t use WebSQL it’s deprecated, use the polyfill. bit.ly/idbpolyfill
- 49. • Origins can have multiple IndexedDB databases • Each database can have multiple ‘object stores’ (like SQL tables) • An object store must have at least one index – IDB is NoSQL – can only be queried by pre-defined indexes • No free text search
- 50. function databaseOpen() {! ! return new Promise(function(resolve, reject) {! ! ! var version = 1;! ! ! var request = indexedDB.open('todos', version);! ! ! request.onupgradeneeded = function(e) {! ! ! ! db = e.target.result;! ! ! ! e.target.transaction.onerror = reject;! ! ! ! db.createObjectStore('todo', {! ! ! ! ! keyPath: '_id'! ! ! ! });! ! ! };! ! ! request.onsuccess = function(e) {! ! ! ! db = e.target.result;! ! ! ! resolve();! ! ! };! ! ! request.onerror = reject;! ! });! } raw javascript
- 51. Highly recommend Dexie.org, a Promise-based IndexedDB library
- 52. function databaseOpen() {! ! var db = new Dexie('todos');! ! db.version(1).stores({ todo: '_id' });! ! return db.open();! } with Dexie.org
- 53. Summary • Service Worker is coming so get ready:- https, Promises, Caches Polyfill … • Use the Fetch API in your applications today bit.ly/iso-fetch / github.com/github/fetch • Want to use IDB? Use dexie.org. Want to support WebSQL? Use the polyfill bit.ly/idbpolyfill. • I’ve written tutorials on how to use all the HTML5 offline tech available for free here:- bit.ly/offline-workshop
- 54. Thanks! • Open Source:- github.com/ftlabs FastClick, Polyfill.io, DOM Delegate, Ellipsis, & more • Jobs:- labs.ft.com/jobs • Me:- @andrewsmatt / mattandre.ws