practical html5

Practical HTML5

Maurice de Beijer

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Who am I?

• Maurice de Beijer• The Problem Solver• Microsoft Integration MVP• DevelopMentor instructor• Twitter:@mauricedb• Blog: http://msmvps.com/blogs/theproblemsolver/ • Web: http://www.HTML5Support.nl • E-mail: mauricedb@develop.com

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What are we going to cover?

• Polyfills• Semantic elements• WebSockets• Drag/Drop• Graphics• Storing data in the browser

• Demos at: http://bit.ly/lph5

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Polyfills

• Not every browser supports every HTML5 feature– Especially true with old browsers

• Many missing features can be added using a polyfill– Offers the standard API– Often done in JavaScript– JavaScript is slow in older browsers

• A few good lists to check– Modernizr HTML5 Cross Browser Polyfills– HTML5 please

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HTML5 Semantic elements

• New HTML5 elements– <nav>– <section>– <header>– <footer>– <article>– <aside>

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HTML5 Semantic elements

• How about support?

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HTML5 Semantic elements

• Why use them?– Searchability– Accessibility

• Neither really makes sense– Search engines don’t really care– Use WAI-ARIA for accessibility support

• Make sure to add support in older versions of IE– Modernizr– Html5Shiv

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HTML5 Semantic elements

• The new HTML5 input elements– <input type="email"/>– <input type="number"/>– <input type="url"/>– <input type="date"/>– <input type="datetime"/>– <input type="month"/>– <input type="week"/>– …..

• Support is not very good, only really useful on mobile devices

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HTML5 Semantic elements

• Other more useful HTML5 elements– <video>– <audio>– <meter>– <progress>– <time>

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WebSockets

• A bi-directional socket connection– Between a web browser and the web server

• The server can push updates to the browser– Refreshing the browser to see updates is so 2012

• Not just for games and chat applications– Any application where you want fast updates– Decrease the chance of concurrency issues

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WebSockets

• How about support?

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WebSockets

• Suffers from lack of infrastructure support– Routers and firewalls can cause issues

• The API is low level– Messages are just simple objects– You might need to retransmit missed messages

• Use ASP.NET SignalR– Uses WebSockets if possible– Otherwise it uses fallbacks like Comet– Supports scale out scenarios– Uses a very simple API

• Using Node.js?– Use Socket.IO instead

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Drag and Drop

• Drag and drop can be a very intuitive user interaction– Often seen as more fun by users

• Very common interaction on tablets– But works equally well with a mouse

• HTML5 supports drag and drop– Including dragging from the file system

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Drag and Drop

How about support?

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Drag and Drop

• Use jQuery UI instead of the HTML5 capabilities– Use jQuery UI Touch Punch for touch support– Add -ms-touch-action: none in CSS for Windows 8

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Graphics

• Rich graphics are common in modern applications– Interactive graphics– Charts

• Often generated on the client– Not just images downloaded from the server

• Two basic options– Scalable Vector Graphics– Canvas

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Comparison of Canvas and SVG

Canvas SVG

Pixel-based (canvas is essentially an image element with a drawing API)

Object Model-based (SVG elements are similar to HTML elements)

Single HTML element similar to <img> in behavior

Multiple graphical elements which become part of the Document Object Model (DOM)

Visual presentation created and modified programmatically through script

Visual presentation created with markup and modified by CSS or programmatically through script

Event model/user interaction is coarse—at the canvas element only; interactions must be manually programmed from mouse coordinates

Event model/user interaction is object-based at the level of primitive graphic elements—lines, rectangles, paths

API does not support accessibility; markup-based techniques must be used in addition to canvas

SVG markup and object model directly supports accessibility

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SVG

• How about support?

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Canvas

• How about support?

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Graphics

• Use a library to make the API easier– Don’t worry about Canvas versus SVG

• jqPlot is great for charts– It uses canvas– Includes exCanvas for IE 7/8 support

• Raphaël is a great choice for general graphics– It uses SVG– Uses VML for IE 7/8 support

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Storing data in the browser

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IndexedDB

• How about support?

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LocalStorage

• How about support?

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Storing data in the browser

• LocalStorage is well supported– Except in very old versions of IE

• IndexedDB is much more powerful– But the API is hard to use

• Lawnchair is easy to use– Abstracts the underlying data storage– Can use LocalStorage, IndexedDB or other storage

• db.js makes IndexedDB easy to use– But requires a polyfill in old browsers

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Conclusion

• There is lots of goodness in HTML5– But not everything is as useful

• Some of the API’s are hard to use– But there are good libraries to make things easier

• Think about supporting older browsers– Use polyfills where needed

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Questions

?The presentation and source code will be available

http://msmvps.com/blogs/theproblemsolver/