Cross platform web app development

Cross platform web app development Tomás Pérez - @tomasperezv José M. Pérez - @jmperezperez

Cross platform application development Contents Web development in Spotify - Why and how - Benefits and learnings Key web technologies that we use - IFrames and postMessage: security and performance - Communication between different tabs Summary Questions

Cross platform application development Spotify <3 web

Cross platform application development Beginnings of Spotify

Cross platform application development Giving web a try ● Using CEF to move features to web ● Write features as webapps ● Sandboxed environment

Cross platform application development Giving web a try (2)

Cross platform application development What is a Spotify app? ● HTML ● CSS ● JS ● manifest.json

Cross platform application development What is a Spotify app? - Developer tools

Cross platform application development Architecture of the Spotify Apps Platform - overview

Cross platform application development Architecture of the Spotify Apps Platform - desktop

Cross platform application development Architecture of the Platform - all clients

Cross platform application development Multiple platforms CapturFiles_25.png

Cross platform application development Releasing Spotify Apps ● Decoupled system ● Provides gradual roll-out, and availability depending on platform and country

Cross platform application development Benefits ● Feature ownership by teams ● Fast development pace due to fewer dependencies ● Less hassle to deploy. Makes it easy to tweak a feature after being released ● 3rd party app development

Cross platform application development Only benefits? ● Performance in views with a lot of data on mobile ● Time to render

Spotify Embedded Platform Tomás Pérez twitter.com/tomasperezv github.com/tomasperezv

Cross platform application development Spotify Embedded Platform

Cross platform application development Content Platform architecture - IFrames and postMessage: security and performance Remote control technology - Communication between different tabs - Performance of the communication channel Performance improvements

Cross platform application development Architecture of the Platform

Cross platform application development Sandboxed platform using IFrames Good - Separated execution context - Better security and privacy - We control the release process Bad - More difficult communication - IFrames are expensive

Cross platform application development How expensive are IFrames? A lot(): () http://www.stevesouders.com/blog/2009/06/03/using-iframes-sparingly/

Cross platform application development Custom widgets in partner pages

Cross platform application development Cross-origin communication using postMessage

Cross platform application development Sending: content of the message frame.contentWindow.postMessage(message, ...); msg [in] Type: any One of the following: ● JavaScript primitive, such as a string ● object ● Array ● ... (*)[object Object]

Cross platform application development Security frame.contentWindow .postMessage(..., 'https://embed.spotify.com'); window.addEventListener('message', function(messageEvt) { if (messageEvt.origin === 'https://valid-domain.com') { ... } });

Cross platform application development postMessage transfer rate

Cross platform application development Remote controlling Spotify Clients Client Desktop: based on long polling + https Webplayer: communication with another browser window or tab - server side - postMessage - Cookies - localStorage

Cross platform application development Is localStorage always available? window.localStorage localStorage.setItem('key', 'value') Storage DOMException constructor: StorageConstructor code: 22 length: 0 constructor: DOMExceptionConstructor message: "QUOTA_EXCEEDED_ERR: DOM Exception 22"

Cross platform application development Communication between different tabs

Cross platform application development localStorage locks The UI Thread is stopped for some operations Firefox and Chrome wait until the first read is requested, then load all the items http://calendar.perfplanet.com/2012/is-localstorage-performance-a-problem/

Cross platform application development localStorage notifications via the storage event window.addEventListener('storage', function() {}, false); The event change is only emitted when the values actually change: use a timestamp if needed. {key: 'command', value: 'play', timestamp: 1373021690574}

Cross platform application development Can we trigger the event manually? var evt = document.createEvent('StorageEvent'); evt.initStorageEvent('storage', ...); window.dispatchEvent(evt); Yes...although not to communicate between different windows.

Cross platform application development localStorage communication strategies Options: A) Create a new item every time, but remove it once it’s received. B) New item, don't remove once it’s received, instead do it regularly. C) Reuse always the same item (use timestamp)

Cross platform application development Notification delay Chrome ~2 milliseconds IE10 ~34 milliseconds

Cross platform application development Performance improvements Prefetch / Prerender ● ● Rendering pages <link rel="prerender" href="..."> Fetching static resources <link rel="prefetch" href="...">

Cross platform application development Potential improvements Batching postMessages Webworkers

Cross platform application development Conclusions - Web apps have been a good choice to extend our functionality in multiple platforms. - Web technologies make relatively easy to create complex integrations to improve the user experience. - It is very important to monitor and analyze carefully the performance.

Cross platform application development Questions? Tomás Pérez @tomasperezv José M. Pérez @jmperezperez Slides, code examples and reference github.com/tomasperezv/spainjs-2013

Cross platform application development Thanks!