Using HTML5 to Build Offline Applications Woody Pewitt Icenium Evangelist @woodyp firstname.lastname@example.org
Features that make HTML5 offline web apps a reality• Application cache• Online/Offline events• localStorage• Web SQL & indexed database
Application cache• Offline browsing• Speed• Reduced server load
App Cache Via. Cache Manifest CACHE MANIFEST # version 0.4 # Files to cache<html manifest="demo.manifest">... CACHE:</html> favicon.ico index.html onlinedemo.html fallback.html Content/jquery.mobile-1.1.1.min.css Scripts/jquery-1.6.4.min.js Scripts/jquery.mobile-1.1.1.js Content/images/ajax-loader.gif Manifest file must be served Content/images/icons-18-white.png with the mime-type “text/cache-manifest” NETWORK: * FALLBACK: http://manifest-validator.com/ *.html fallback.html
Online/Offline events• checking • Fired once when the app reads the manifest file to see if it has changed.• noupdate • The manifest file has not changed.• downloading • Files are being downloaded• progress • Fired once per each file downloaded. If you have 15 files, you’ll see 15 progress events. Unfortunately, the event itself doesn’t contain information about which file just completed, so it’s fairly limited in its current form.• cached • Files have finished downloading.• updateready • A new copy of the cache is ready to be swapped in.• obsolete • The manifest file is code 404 or code 410; the application cache for the site has been deleted.• error • An error occurred when loading the manifest, its parent page, or a listed resource, or the manifest file changed while the update was running. The cache update has been aborted.
Web Storage• localStorage & sessionStorage• Supported on all modern browsers• Simple API & usage• Semantic events available• Poor performance with large/complex data • searching, storing and retrieving
Web SQL Database• Supported on major mobile browsers • Android Browser, Mobile Safari, Opera Mobile & several desktop browsers• Good performance generally • Asynchronous API (Synchronous API is also available for WebWorkers.)• Good search performance• Robust • Supports a transactional database model• Easier to maintain integrity of data, due to rigid data structure.
IndexedDB• Arisen from experiences with both Web Storage & Web SQL Database• Can be seen as an attempt to combine their strengths without incurring their weaknesses• Asynchronous API• Indexes
File Access• Can store large content and binary files • images, audio, video, PDFs, etc.• Good performance • Asynchronous API• Very early standard• No transaction support• No built-in search/indexing support