People don't give a f**k of JavaScript - Dutch Mobile Conference 2014

People don't give a f**k of JavaScript - Dutch Mobile Conference 2014

People don't give a f**k of JavaScript. You shouldn't either. We are here to do stuffs, whether you call them websites, web applications, web services or hybrid apps. People want to perform tasks, not listen you talking about your favourite programming language. So, use the one you feel more comfortable with and just release the next big thing. But, if your favourite language is JavaScript, let's write better code. What does better means? Better for developers, better for devices, better for users.

In this talk, I'll describe some of the latest HTML5 APIs, many of which still experimental, that can help you develop great code. In a bunch of minutes, you'll see how to use:

- The High Resolution Time and the User Timing APIs to help yourself testing your code performances
- The Page Visibility and the Battery APIs to take care of devices' resources
- The Vibration and the GetUserMedia APIs to create better User Experiences

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Aurelio De Rosa

June 27, 2014
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Transcript

  1. 1.

    PEOPLE DON'T GIVE A F**K OF JAVASCRIPT Aurelio De Rosa

    Amsterdam, Netherlands - 27 June 2014
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    3 QUESTIONS FOR YOU 1. Do you think they understand

    programming languages? 2. Do you think they know what's JavaScript? 3. Do you think they care about JavaScript?
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    “I'm a Java developer and I don't think I would

    trust a PHP developer enough to teach me something about the web” — Anonymous
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    “There are only two kinds of languages: the ones people

    complain about and the ones nobody uses” — Bjarne Stroustrup
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    “Pick one that feels right to you, and start building

    things. That's all that matters.” — Jeffrey Way
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    PATTERN OF THE NEXT PART What Use Cases Methods, Properties

    and Events Example Browsers' Support (Desktop and Mobile) Use it today (Polyfills) Demo (live)
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    DON'T BELIEVE ME? LOOK AT THIS SNIPPET v a r

    s t a r t T i m e = D a t e . n o w ( ) ; / / A t i m e c o n s u m i n g f u n c t i o n f o o ( ) ; v a r t e s t 1 = D a t e . n o w ( ) ; / / A n o t h e r t i m e c o n s u m i n g f u n c t i o n b a r ( ) ; v a r t e s t 2 = D a t e . n o w ( ) ; / / P r i n t r e s u l t s c o n s o l e . d e b u g ( " T e s t 1 t i m e : " + ( t e s t 1 - s t a r t T i m e ) ) ; c o n s o l e . d e b u g ( " T e s t 2 t i m e : " + ( t e s t 2 - t e s t 1 ) ) ;
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    WHAT'S WRONG WITH DATE.NOW()? 1. It is not monotonically increasing

    2. Milliseconds precision 3. Precision of this timestamp varies between user agents 4. Different scope
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    WHAT IT DOES? Allows to accurately retrieve the number of

    milliseconds from the n a v i g a t i o n S t a r t attribute (belongs to the ). Navigation Timing API
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    USE CASES Work with animation at high FPS rate Ensure

    a perfect audio-video synchronization
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    EXAMPLE v a r s t a r t T

    i m e = p e r f o r m a n c e . n o w ( ) ; / / A t i m e c o n s u m i n g f u n c t i o n f o o ( ) ; v a r t e s t 1 = p e r f o r m a n c e . n o w ( ) ; / / A n o t h e r t i m e c o n s u m i n g f u n c t i o n b a r ( ) ; v a r t e s t 2 = p e r f o r m a n c e . n o w ( ) ; / / P r i n t r e s u l t s c o n s o l e . d e b u g ( " T e s t 1 t i m e : " + ( t e s t 1 - s t a r t T i m e ) ) ; c o n s o l e . d e b u g ( " T e s t 2 t i m e : " + ( t e s t 2 - t e s t 1 ) ) ;
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    DESKTOP BROWSERS' SUPPORT Explorer Chrome* Safari Firefox Opera 10+ 20+

    (-webkit) 24+ None 15+ 15+ Data updated to 21st June 2014 * As for now, p e r f o r m a n c e . n o w ( ) in Chrome on Windows returns a time almost always near the very start or the very end of a second ( ). issue #158234
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    MOBILE BROWSERS' SUPPORT Explorer Android Chrome Safari Firefox Opera* 10+

    4.4+ 24+ None 15+ None Data updated to 21st June 2014 * Opera in the Mobile Browsers' support tables stand for Opera Mini
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    HOW TO USE IT NOW w i n d o

    w . p e r f o r m a n c e = w i n d o w . p e r f o r m a n c e | | { } ; p e r f o r m a n c e . n o w = p e r f o r m a n c e . n o w | | f u n c t i o n ( ) { r e t u r n D a t e . n o w ( ) ; } ;
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    METHODS m a r k ( ) c l e

    a r M a r k s ( ) m e a s u r e ( ) c l e a r M e a s u r e s ( ) g e t E n t r i e s B y T y p e ( ) g e t E n t r i e s B y N a m e ( )
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    PROPERTIES n a m e e n t r y

    T y p e s t a r t T i m e d u r a t i o n
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    EXAMPLE p e r f o r m a n

    c e . m a r k ( ' s t a r t T i m e 1 ' ) ; f o o ( ) ; p e r f o r m a n c e . m a r k ( ' e n d T i m e 1 ' ) p e r f o r m a n c e . m a r k ( ' s t a r t T i m e 2 ' ) ; b a r ( ) ; p e r f o r m a n c e . m a r k ( ' e n d T i m e 2 ' ) ; p e r f o r m a n c e . m e a s u r e ( ' d u r a t i o n T i m e 1 ' , ' s t a r t T i m e 1 ' , ' e n d T i m e 1 ' ) ; p e r f o r m a n c e . m e a s u r e ( ' d u r a t i o n T i m e 2 ' , ' s t a r t T i m e 2 ' , ' e n d T i m e 2 ' ) ; p e r f M e a s u r e s = p e r f o r m a n c e . g e t E n t r i e s B y T y p e ( ' m e a s u r e ' ) ; f o r ( v a r i = 0 ; i < p e r f M e a s u r e s . l e n g t h ; i + + ) { c o n s o l e . l o g ( ' N a m e : ' + p e r f M e a s u r e s [ i ] . n a m e + ' - ' + ' D u r a t i o n : ' + p e r f M e a s u r e s [ i ] . d u r a t i o n + ' \ n ' ) ; }
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    DESKTOP BROWSERS' SUPPORT Explorer Chrome Safari Firefox Opera 10+ 25+

    None None 15+ Data updated to 21st June 2014
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    MOBILE BROWSERS' SUPPORT Explorer Android Chrome Safari Firefox Opera 10+

    4.4+ 25+ None None None Data updated to 21st June 2014
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    WHAT IT DOES? Provides information about the page visibility's status

    Fires events about changes of the page visibility's status
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    USE CASES Stop sending requests to the server for updates

    Pause a video or a song Stop the time counter of an intermediate ads page
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    PROPERTIES h i d d e n v i s

    i b i l i t y S t a t e (h i d d e n , v i s i b l e , p r e r e n d e r , u n l o a d e d )
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    EVENTS The only event exposed is v i s i

    b i l i t y c h a n g e .
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    EXAMPLE v a r v i e w s =

    0 ; v a r c o u n t V i e w s = f u n c t i o n ( ) { i f ( d o c u m e n t . h i d d e n = = = f a l s e ) { v i e w s + + ; c o n s o l e . l o g ( " V i s i t " + v i e w s ) ; } } ; / / R u n t h e f u n c t i o n t h e f i r s t t i m e c o u n t V i e w s ( ) ; / / L i s t e n f o r v i s i b i l i t y c h a n g e d o c u m e n t . a d d E v e n t L i s t e n e r ( " v i s i b i l i t y c h a n g e " , c o u n t V i e w s , f a l s e ) ;
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    DESKTOP BROWSERS' SUPPORT Explorer Chrome Safari Firefox Opera 10+ 14+

    (-webkit) 33+ 6.1+ 10+ (-moz) 18+ 12.10+ 15+ (-webkit) 20+ Data updated to 21st June 2014
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    MOBILE BROWSERS' SUPPORT Explorer Android Chrome Safari Firefox Opera 10+

    4.4+ 13+ (-webkit) 33+ 7.0+ 10+ (-moz) 18+ None Data updated to 21st June 2014
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    WHAT IT DOES? Provides information about the system's battery charge

    level Fires events about changes of the battery level or status
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    USE CASES Slow down a process Save changes more frequently

    to prevent data loss Deny to start a critical and time consuming process
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    PROPERTIES c h a r g i n g c

    h a r g i n g T i m e d i s c h a r g i n g T i m e l e v e l
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    EVENTS c h a r g i n g c

    h a n g e c h a r g i n g t i m e c h a n g e d i s c h a r g i n g t i m e c h a n g e l e v e l c h a n g e
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    EXAMPLE / / P r i n t i f

    b a t t e r y i s c h a r g i n g o r n o t c o n s o l e . l o g ( " T h e d e v i c e ' s b a t t e r y i s " + ( n a v i g a t o r . b a t t e r y . c h a r g i n g ? " " : " n o t " ) + " c h a r g i n g " ) ; / / P r i n t t h e c u r r e n t b a t t e r y l e v e l c o n s o l e . l o g ( " T h e l e v e l o f t h e b a t t e r y i s " + ( n a v i g a t o r . b a t t e r y . l e v e l ? ( n a v i g a t o r . b a t t e r y . l e v e l * 1 0 0 ) + " % " : " U N K N O W N " ) ) ;
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    DESKTOP BROWSERS' SUPPORT Explorer Chrome Safari Firefox Opera None None

    None 10+ (-moz) 16+ None Data updated to 21st June 2014
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    MOBILE BROWSERS' SUPPORT Explorer Android Chrome Safari Firefox Opera None

    None None None 10+ (-moz) 16+ None Data updated to 21st June 2014
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    EXAMPLE / / V i b r a t e

    o n c e f o r 1 s e c o n d n a v i g a t o r . v i b r a t e ( 1 0 0 0 ) ; / / V i b r a t e t h r i c e . T w o t i m e s f o r 1 s e c o n d , w i t h a h a l f / / s e c o n d i n t e r v a l , a n d t h e n v i b r a t e f o r 2 s e c o n d s n a v i g a t o r . v i b r a t e ( [ 1 0 0 0 , 5 0 0 , 1 0 0 0 , 5 0 0 , 2 0 0 0 ] ) ; / / C a n c e l l i n g V i b r a t i o n s n a v i g a t o r . v i b r a t e ( 0 ) ;
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    DESKTOP BROWSERS' SUPPORT Explorer Chrome Safari Firefox Opera None 30+*

    32+ None 11+ (-moz) 16+ 17+* 19+ Data updated to 21st June 2014 * You have to activate the flag Experimental Web Platform features
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    MOBILE BROWSERS' SUPPORT Explorer Android Chrome Safari Firefox Opera None

    4.4+ 30+* 32+ None 11+ (-moz) 16+ None Data updated to 21st June 2014 * You have to activate the flag Experimental Web Platform features
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    EXAMPLE < v i d e o i d =

    " v i d e o " a u t o p l a y = " a u t o p l a y " c o n t r o l s = " t r u e " > < / v i d e o > < s c r i p t > v a r v i d e o = d o c u m e n t . g e t E l e m e n t B y I d ( " v i d e o " ) ; n a v i g a t o r . g e t U s e r M e d i a ( { v i d e o : t r u e , a u d i o : t r u e } , f u n c t i o n ( s t r e a m ) { v i d e o . s r c = s t r e a m ; v i d e o . p l a y ( ) ; } , f u n c t i o n ( e r r o r ) { c o n s o l e . l o g ( ' V i d e o c a p t u r e e r r o r : ' + e r r o r . c o d e ) ; } ) ; < / s c r i p t >
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    DESKTOP BROWSERS' SUPPORT Explorer Chrome Safari Firefox Opera None 21+

    (-webkit) None 17+ (-moz) 12+ 15+ (None) 18+ (-webkit) Data updated to 21st June 2014
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    MOBILE BROWSERS' SUPPORT Explorer Android Chrome Safari Firefox Opera None

    None 21+ (-webkit) None 24+ (-moz) None Data updated to 21st June 2014
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    TO LEARN MORE... ABOUT THESE AND OTHER APIS HTML5 API

    DEMOS https://github.com/AurelioDeRosa/HTML5-API-demos A repository I created and maintain. It contains a collection of demos that allows to play with some of the APIs introduced in HTML5.
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    CONCLUSIONS Future of web development is bright ...but some browsers

    aren't prepared yet Focus on goals, not technologies Take care of performances Take care of devices' resources Take care of your users' experience
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