People don't give a f**k of JavaScript - London Web Standards July 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

Transcript

1. PEOPLE DON'T GIVE A F**K OF JAVASCRIPT Aurelio De Rosa London, United Kingdom - 21 July 2014
2. WEB & APP DEVELOPER CONTRIBUTE(D) TO ... jQuery CanIUse PureCSS WRITE FOR SitePoint.com Tuts+.com ModernWeb.com (formerly FlippinAwesome.com)
3. AUTHORED BOOKS JQUERY IN ACTION (3RD EDITION) INSTANT JQUERY SELECTORS (Shameless self-promotion!)
5. WHO ARE YOUR USERS?
10. 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?
11. ...BUT I'M A DEVELOPER!
13. TASK
14. EXPERIENCE
15. “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
16. “There are only two kinds of languages: the ones people complain about and the ones nobody uses” — Bjarne Stroustrup
17. “Pick one that feels right to you, and start building things. That's all that matters.” — Jeffrey Way
19. LET'S WRITE BETTER JAVASCRIPT
20. PATTERN OF THE NEXT PART What Use Cases Methods, Properties and Events Example Browsers Support (Desktop and Mobile) Use it today (Polyfills) Demo (live)
21. ...Better for Developers
22. PERFORMANCE MATTERS!
23. Reference: http://torbit.com/blog/2012/09/19/some-interesting-performance-statistics/
24. Reference: http://torbit.com/blog/2012/09/19/some-interesting-performance-statistics/
25. LESSON: TEST AND IMPROVE YOUR WEBSITE'S PERFORMANCE
26. HOW WE USE TO TEST PERFORMANCE
27. 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 ) ) ;
28. 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
29. OK, I GOT IT. NOW WHAT?
30. HIGH RESOLUTION TIME API
31. 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
32. USE CASES Work with animation at high FPS rate Ensure a perfect audio-video synchronization
33. METHODS The only method exposed is n o w ( ) .
34. 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 ) ) ;
35. BROWSERS SUPPORT
36. DESKTOP BROWSERS SUPPORT Explorer Chrome* Safari Firefox Opera* 10+ 20+ (-webkit) 24+ None 15+ 15+ Data updated to 19th July 2014 * As for now, p e r f o r m a n c e . n o w ( ) in Chrome and Opera on Windows returns a time almost always near the very start or the very end of a millisecond ( ). Chrome issue #158234
37. MOBILE BROWSERS SUPPORT Explorer Android Chrome Safari Firefox Opera* 10+ 4.4+ 24+ None 15+ None Data updated to 19th July 2014 * Opera in the Mobile Browsers support tables stand for Opera Mini
38. 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 ( ) ; } ;
39. TOO MANY VARS!
40. USER TIMING API
41. WHAT IT DOES? Allows to accurately measure and store performance of a JavaScript code
42. USE CASES Performance testing
43. 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 ( )
44. 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
45. 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 ' ) ; }
46. BROWSERS SUPPORT
47. DESKTOP BROWSERS SUPPORT Explorer Chrome Safari Firefox Opera 10+ 25+ None None 15+ Data updated to 19th July 2014
48. MOBILE BROWSERS SUPPORT Explorer Android Chrome Safari Firefox Opera 10+ 4.4+ 25+ None None None Data updated to 19th July 2014
49. HOW TO USE IT NOW usertiming.js
50. ...Better for Devices
51. PAGE VISIBILITY API
52. WHAT IT DOES? Provides information about the page visibility's status Fires events about changes of the page visibility's status
53. 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
54. 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 )
55. EVENTS The only event exposed is v i s i b i l i t y c h a n g e .
56. 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 ) ;
57. BROWSERS SUPPORT
58. 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 19th July 2014
59. MOBILE BROWSERS SUPPORT Explorer Android Chrome Safari Firefox Opera 10+ 4.4+ (-webkit) 13+ (-webkit) 33+ 7.0+ 10+ (-moz) 18+ None Data updated to 19th July 2014
60. HOW TO USE IT NOW visibly.js Visibility.js
61. BATTERY STATUS API
62. WHAT IT DOES? Provides information about the system's battery charge level Fires events about changes of the battery level or status
63. USE CASES Slow down a process Save changes more frequently to prevent data loss Deny to start a critical and time consuming process
64. 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
65. 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
66. 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 " ) ) ;
67. BROWSERS SUPPORT
68. DESKTOP BROWSERS SUPPORT Explorer Chrome Safari Firefox Opera None None None 10+ (-moz) 16+ None Data updated to 19th July 2014
69. MOBILE BROWSERS SUPPORT Explorer Android Chrome Safari Firefox Opera None None None None 10+ (-moz) 16+ None Data updated to 19th July 2014
70. HOW TO USE IT NOW NO POLYFILL AVAILABLE
71. ...Better for Users
72. VIBRATION API
73. WHAT IT DOES? Provides tactile feedback
74. USE CASES
75. Vibrate on an explosion in a movie
76. Vibrate when someone punches you in a fighting game
77. Vibrate when in a racing game a car crashes
78. METHODS The only method exposed is v i b r a t e ( ) .
79. 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 ) ;
80. BROWSERS SUPPORT
81. DESKTOP BROWSERS SUPPORT Explorer Chrome Safari Firefox Opera None 30+* 32+ None 11+ (-moz) 16+ 17+* 19+ Data updated to 19th July 2014 * You have to activate the flag Experimental Web Platform features
82. MOBILE BROWSERS SUPPORT Explorer Android Chrome Safari Firefox Opera None 4.4+ 30+* 32+ None 11+ (-moz) 16+ None Data updated to 19th July 2014 * You have to activate the flag Experimental Web Platform features
83. HOW TO USE IT NOW NO POLYFILL AVAILABLE
84. TO BE HONEST... mozVibrate-polyfill
85. GETUSERMEDIA API
86. WHAT IT DOES? Provides access to multimedia streams (video, audio, or both) from local devices
87. USE CASES
88. Real-time communication (chat)
89. Recording tutorial or lesson for online courses
90. Home or work surveillance
91. METHODS The only method exposed is g e t U s e r M e d i a ( ) .
92. 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 >
93. BROWSERS SUPPORT
94. DESKTOP BROWSERS SUPPORT Explorer Chrome Safari Firefox Opera None 21+ (-webkit) None 17+ (-moz) 12+ 15+ (None) 18+ (-webkit) Data updated to 19th July 2014
95. MOBILE BROWSERS SUPPORT Explorer Android Chrome Safari Firefox Opera None None 21+ (-webkit) None 24+ (-moz) None Data updated to 19th July 2014
96. HOW TO USE IT NOW getUserMedia.js
97. DO YOU LIKE APIS? OF COURSE YOU DO! Ambient Light API Device Orientation API Geolocation API Network Information API Proximity API Speech Synthesis API Web Notification API Web Speech API ...
98. 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.
99. 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
100. THANK YOU!
101. QUESTIONS?
102. CONTACTS Website: Email: Twitter: www.audero.it a.derosa@audero.it @AurelioDeRosa