ECMAScript 6 In Depth - Part II

A talk I gave to the Santa Barbara JavaScript Meetup, June 23rd, 2015.

Transcript

1. ECMASCRIPT 6 IN DEPTH
2. PREVIOUSLY IN ECMASCRIPT 6 IN DEPTH ...or, when last we saw our hero...
3. JavaScript
4. ES6 is the first major language update in over 15 years New syntax aimed at reducing boilerplate JavaScript now has "classes" (but not really) Native modules for organizing code JavaScript is King of the web
6. MEANWHILE Spec ratified and published June 17th, 2015 Now the official language standard WebAssembly ("wasm")
7. PART II Enhanced Built-ins Object Array String Symbols Iterators + for...of Generators
8. OBJECT STATIC METHODS
9. l e t o b j 1 = { f o o : ' 1 ' } ; l e t o b j 2 = { b a r : ' 2 ' } ; O b j e c t . a s s i g n ( o b j 1 , o b j 2 ) ; / / o r l e t o b j 1 = O b j e c t . a s s i g n ( { f o o : ' 1 ' } , o b j 2 ) ; o b j 1 / / { f o o : ' 1 ' , b a r : ' 2 ' }
10. l e t o b j 1 = O b j e c t . c r e a t e ( { b a r : ' b a z ' } ) ; o b j 1 . f o o = ' b a r ' ; l e t o 1 P r o t o = O b j e c t . g e t P r o t o t y p e O f ( o b j 1 ) ; l e t o b j 2 = O b j e c t . a s s i g n ( O b j e c t . c r e a t e ( o 1 P r o t o ) , o b j 1 ) ; o b j 2 . b a r / / ' b a z '
11. / / E S 5 N a N = = = N a N / / f a l s e / / E S 6 O b j e c t . i s ( N a N , N a N ) / / t r u e / / E S 5 0 = = = - 0 / / t r u e / / E S 6 O b j e c t . i s ( 0 , - 0 ) / / f a l s e
12. l e t o b j = { [ S y m b o l ( ' a ' ) ] : ' l o c a l S y m b o l ' , [ S y m b o l . f o r ( ' b ' ) ] : ' g l o b a l S y m b o l ' } ; l e t s = O b j e c t . g e t O w n P r o p e r t y S y m b o l s ( o b j ) ; s . l e n g t h / / 2 s / / [ S y m b o l ( a ) , S y m b o l ( b ) ] s [ 0 ] / / S y m b o l ( a )
13. l e t o b j 1 = { f o o ( ) { r e t u r n ' b a r ' ; } } ; l e t o b j 2 = { b a r : ' 2 ' } O b j e c t . s e t P r o t o t y p e O f ( o b j 2 , o b j 1 ) ; o b j 2 . f o o ( ) / / ' b a r ' * O b j e c t . c r e a t e ( ) i s i s s t i l l p r e f e r r e d
14. ARRAY STATIC METHODS
15. A r r a y . o f ( 1 ) ; / / [ 1 ] A r r a y . o f ( 1 , 2 , 3 ) ; / / [ 1 , 2 , 3 ] A r r a y . o f ( u n d e f i n e d ) ; / / [ u n d e f i n e d ]
16. A r r a y . f r o m ( ' f o o ' ) ; / / [ ' f ' , ' o ' , ' o ' ] A r r a y . f r o m ( [ 1 , 2 , 3 ] , x = > x * x ) ; / / [ 1 , 4 , 9 ] f u n c t i o n f ( ) { r e t u r n A r r a y . f r o m ( a r g u m e n t s ) ; } f ( 1 , 2 , 3 ) ; / / [ 1 , 2 , 3 ] A r r a y . f r o m ( { l e n g t h : 5 } , ( v , i ) = > i ) ; / / [ 0 , 1 , 2 , 3 , 4 ]
17. ARRAY PROTOTYPE METHODS
18. l e t a r r = [ { n a m e : ' f o o ' , v a l : ' 1 ' } , { n a m e : ' b a r ' , v a l : ' 2 ' } , { n a m e : ' b a z ' , v a l : ' 3 ' } ] ; / / E S 5 f u n c t i o n f i n d ( a r r , p r o p , v a l u e ) { v a r l e n = = a r r . l e n g t h ; w h i l e ( l e n - - ) { i f ( a r r [ l e n ] [ p r o p ] = = = v a l u e ) { r e t u r n a r r [ l e n ] ; } } } / / E S 6 a r r . f i n d ( e = > e . v a l = = = ' 2 ' ) ;
19. l e t a r r = [ { n a m e : ' f o o ' , v a l : ' 1 ' } , { n a m e : ' b a r ' , v a l : ' 2 ' } , { n a m e : ' b a z ' , v a l : ' 3 ' } ] ; / / E S 5 f u n c t i o n f i n d I n d e x ( a r r , p r o p , v a l u e ) { v a r l e n = = a r r . l e n g t h ; w h i l e ( l e n - - ) { i f ( a r r [ l e n ] [ p r o p ] = = = v a l u e ) { r e t u r n l e n ; } } } / / E S 6 a r r . f i n d I n d e x ( e = > e . v a l = = = ' 2 ' ) ;
20. [ 1 , 2 , 3 , 4 , 5 ] . c o p y W i t h i n ( 0 , 3 ) ; / / [ 4 , 5 , 3 , 4 , 5 ] [ 1 , 2 , 3 , 4 , 5 ] . c o p y W i t h i n ( 0 , 3 , 4 ) ; / / [ 4 , 2 , 3 , 4 , 5 ] [ 1 , 2 , 3 , 4 , 5 ] . c o p y W i t h i n ( 0 , - 2 , - 1 ) ; / / [ 4 , 2 , 3 , 4 , 5 ] l e t o b j = { l e n g t h : 5 , 3 : 1 } ; [ ] . c o p y W i t h i n . c a l l ( o b j , 0 , 3 ) ; / / { 0 : 1 , 3 : 1 , l e n g t h : 5 }
21. [ 1 , 2 , 3 ] . f i l l ( 4 ) ; / / [ 4 , 4 , 4 ] [ 1 , 2 , 3 ] . f i l l ( 4 , 1 ) ; / / [ 1 , 4 , 4 ] [ 1 , 2 , 3 ] . f i l l ( 4 , 1 , 2 ) ; / / [ 1 , 4 , 3 ] [ 1 , 2 , 3 ] . f i l l ( 4 , - 3 , - 2 ) ; / / [ 4 , 2 , 3 ] [ ] . f i l l . c a l l ( { l e n g t h : 3 } , 4 ) ; / / { 0 : 4 , 1 : 4 , 2 : 4 , l e n g t h : 3 }
22. [ . . . [ 1 , 2 , 3 ] . k e y s ( ) ] ; / / [ 0 , 1 , 2 ] [ . . . [ 1 , 2 , 3 ] . v a l u e s ( ) ] ; / / [ 1 , 2 , 3 ] [ . . . [ 1 , 2 , 3 ] . e n t r i e s ( ) ] ; / / [ [ 0 , 1 ] , [ 1 , 2 ] , [ 2 , 3 ] ]
23. STRING STATIC METHODS
24. S t r i n g . r a w ( ` H e l l o \ n W o r l d ! ` ) ; / / ' H e l l o \ \ n W o r l d ! '
25. S t r i n g . f r o m C o d e P o i n t ( 1 0 2 , 1 1 1 , 1 1 1 ) ; / / ' f o o '
26. STRING PROTOTYPE METHODS
27. l e t s t r = ' G o o d m o r n i n g D a v e . ' ; / / E S 5 s t r . i n d e x O f ( ' m o r n i n g ' ) ! = = - 1 / / t r u e s t r . i n d e x O f ( ' f o o b a r ' ) ! = = - 1 / / f a l s e / / E S 6 s t r . i n c l u d e s ( ' m o r n i n g ' ) / / t r u e s t r . i n c l u d e s ( ' f o o b a r ' ) / / f a l s e
28. l e t s t r = ' G o o d m o r n i n g D a v e . ' ; / / E S 5 s t r . i n d e x O f ( ' G o o d m o r n i n g ' ) = = = 0 / / t r u e / / E S 6 s t r . s t a r t s W i t h ( ' G o o d m o r n i n g ' ) / / t r u e
29. l e t s t r = ' G o o d m o r n i n g D a v e . ' ; / / E S 5 s t r . s u b s t r ( s t r . l e n g t h - ' D a v e . ' . l e n g t h - 1 ) = = = ' D a v e . ' / / t r u e / / E S 6 s t r . e n d s W i t h ( ' D a v e . ' ) / / t r u e
30. / / E S 5 ( n e w A r r a y ( 4 ) ) . j o i n ( ' a ' ) ; / / ' a a a ' / / E S 6 ' a ' . r e p e a t ( 3 ) ; / / ' a a a '
31. ' f o o b a r ' . c o d e P o i n t A t ( 3 ) ; / / 9 8 ' \ u D 8 0 1 \ u D C 3 7 ' . c o d e P o i n t A t ( 0 ) ; / / 6 6 6 1 5
32. ' m a ñ a n a ' = = = ' m a ñ a n a ' / / f a l s e ? ? ? ' m a \ x F 1 a n a ' U + 0 0 F 1 L A T I N S M A L L L E T T E R N W I T H T I L D E ' m a \ u 0 0 6 E \ u 0 3 0 3 a n a ' U + 0 0 6 E L A T I N S M A L L L E T T E R N + U + 0 3 0 3 C O M B I N I N G T I L D E ' m a ñ a n a ' . n o r m a l i z e ( ' N F C ' ) = = = ' m a ñ a n a ' . n o r m a l i z e ( ' N F C ' ) / / t r u e
33. / / E S 5 ' \ u D 8 3 D \ u D C A 9 ' / / U + 1 F 4 A 9 P I L E O F P O O / / E S 6 ' \ u { 1 F 4 A 9 } ' / / U + 1 F 4 A 9 P I L E O F P O O
34. SYMBOLS Unique, immutable type that can be used for property identifiers Symbol object is an implicit wrapper for the primitive type
35. l e t s y m = S y m b o l ( ' f o o ' ) ; / / l o c a l t y p e o f s y m / / ' s y m b o l ' l e t s y m 2 = S y m b o l ( ' f o o ' ) ; s y m = = = s y m 2 / / f a l s e l e t s y m 3 = S y m b o l . f o r ( ' f o o ' ) ; / / g l o b a l
36. l e t s y m = S y m b o l ( ' a ' ) ; l e t o b j = { [ s y m ] : ' f o o ' , b a r : ' b a z ' } ; o b j [ s y m ] / / ' f o o ' O b j e c t . g e t O w n P r o p e r t y N a m e s ( o b j ) / / [ ' b a r ' ] O b j e c t . g e t O w n P r o p e r t y S y m b o l s ( o b j ) / / [ S y m b o l ( a ) ]
37. l e t T h i n g = ( f u n c t i o n ( ) { l e t n a m e S y m b o l = S y m b o l ( ) ; r e t u r n c l a s s T h i n g { c o n s t r u c t o r ( n a m e ) { t h i s [ n a m e S y m b o l ] = n a m e ; } g e t n a m e ( ) { r e t u r n t h i s [ n a m e S y m b o l ] ; } } ; } ) ( ) ; l e t i t = n e w T h i n g ( ' f o o ' ) ; i t . n a m e / / ' f o o ' i t . n a m e = ' b a r ' ; / / T y p e E r r o r O b j e c t . g e t O w n P r o p e r t y N a m e s ( i t ) / / [ ]
38. "WELL-KNOWN" SYMBOLS Symbol.iterator Symbol.match Symbol.replace Symbol.search Symbol.split Symbol.hasInstance Symbol.isConcatSpreadable Symbol.unscopables Symbol.species Symbol.toPrimitive Symbol.toStringTag
39. ITERATORS ES6 introduces an Iterable interface Implemented by built-in collections: Array, String, Set, Map Objects can implement Iterable
40. i n t e r f a c e I t e r a b l e { [ S y m b o l . i t e r a t o r ] ( ) : I t e r a t o r ; } i n t e r f a c e I t e r a t o r { n e x t ( ) : I t e r a t o r R e s u l t ; r e t u r n ? ( v a l u e ? : a n y ) : I t e r a t o r R e s u l t ; } i n t e r f a c e I t e r a t o r R e s u l t { v a l u e : a n y ; d o n e : b o o l e a n ; }
41. l e t a r r = [ 1 , 2 , 3 ] ; l e t i t e r = a r r [ S y m b o l . i t e r a t o r ] ( ) ; i t e r . n e x t ( ) ; / / { v a l u e : 1 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { v a l u e : 2 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { v a l u e : 3 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { v a l u e : u n d e f i n e d , d o n e : t r u e }
42. l e t s t r = ' H e l l o ' ; l e t i t e r = s t r [ S y m b o l . i t e r a t o r ] ( ) ; / / s p r e a d o p e r a t o r c o n s u m e s i t e r a b l e s [ . . . i t e r ] ; / / [ ' H ' , ' e ' , ' l ' , ' l ' , ' o ' ] / / a l t e r n a t e l y [ . . . ' H e l l o ' [ S y m b o l . i t e r a t o r ] ( ) ]
43. FOR...OF Concise syntax for iterating the values of an iterable
44. l e t a r r = [ 1 , 2 , 3 ] ; f o r ( l e t n u m o f a r r ) { c o n s o l e . l o g ( n u m ) ; } / / 1 / / 2 / / 3
45. l e t s t r = ' H e l l o ' ; f o r ( l e t c h r o f s t r ) { c o n s o l e . l o g ( c h r ) ; } / / ' H ' / / ' e ' / / ' l ' / / ' l ' / / ' o '
46. VS. FOR...IN Iterates over property names vs. property values
47. VS. FOREACH() Iteration can be cancelled with `break` statement
48. CUSTOM ITERATORS Objects aren't iterable by default Objects can implement [Symbol.iterator]() to become iterable
49. l e t i t e r a b l e = { [ S y m b o l . i t e r a t o r ] ( ) { v a r n = 3 , i = 1 ; r e t u r n { n e x t ( ) { i f ( i < = n ) { r e t u r n { v a l u e : i , d o n e : f a l s e } ; } r e t u r n { v a l u e : u n d e f i n e d , d o n e : t r u e } ; } } } } ; [ . . . i t e r a b l e ] ; / / [ 1 , 2 , 3 ]
50. GENERATORS Functions that can be paused and resumed Important applications include iterators and async programming
52. THREE MAIN ROLES Iterators (data producers) Observers (data consumers) Coroutines (data producers and consumers)
53. GENERATORS AS ITERATORS
54. f u n c t i o n * i t e r a b l e ( ) { f o r ( l e t i = 1 ; i < 4 ; i + + ) { y i e l d i ; } } l e t i t e r = i t e r a b l e ( ) ;
55. f u n c t i o n * i t e r a b l e ( ) { f o r ( l e t i = 1 ; i < 4 ; i + + ) { y i e l d i ; / / i = 1 < - p a u s e } } l e t i t e r = i t e r a b l e ( ) ; i t e r . n e x t ( ) ; / / { v a l u e : 1 , d o n e : f a l s e }
56. f u n c t i o n * i t e r a b l e ( ) { f o r ( l e t i = 1 ; i < 4 ; i + + ) { y i e l d i ; / / i = 2 < - p a u s e } } l e t i t e r = i t e r a b l e ( ) ; i t e r . n e x t ( ) ; / / { v a l u e : 1 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { v a l u e : 2 , d o n e : f a l s e }
57. f u n c t i o n * i t e r a b l e ( ) { f o r ( l e t i = 1 ; i < 4 ; i + + ) { y i e l d i ; / / i = 3 < - p a u s e } } l e t i t e r = i t e r a b l e ( ) ; i t e r . n e x t ( ) ; / / { v a l u e : 1 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { v a l u e : 2 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { v a l u e : 3 , d o n e : f a l s e }
58. f u n c t i o n * i t e r a b l e ( ) { f o r ( l e t i = 1 ; i < 4 ; i + + ) { / / i = 4 y i e l d i ; } } l e t i t e r = i t e r a b l e ( ) ; i t e r . n e x t ( ) ; / / { v a l u e : 1 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { v a l u e : 2 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { v a l u e : 3 , d o n e : f a l s e } i t e r . n e x t ( ) ; / / { d o n e : t r u e }
59. l e t o b j = { * i t e r a b l e ( ) { f o r ( l e t i = 1 ; i < 4 ; i + + ) { y i e l d i ; } } } ; [ . . . o b j . i t e r a b l e ( ) ] / / [ 1 , 2 , 3 ]
60. COMBINING GENERATORS
61. f u n c t i o n * e v e n ( i t e r a b l e ) { f o r ( l e t n o f i t e r a b l e ) { i f ( n % 2 = = = 0 ) { y i e l d n ; } } } f u n c t i o n * t a k e ( n , i t e r a b l e ) { l e t i t e r = i t e r a b l e [ S y m b o l . i t e r a t o r ] ( ) ; w h i l e ( n - - ) { y i e l d i t e r . n e x t ( ) . v a l u e ; } } l e t a r r = [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ] ; [ . . . t a k e ( 3 , e v e n ( a r r ) ) ] ; / / [ 2 , 4 , 6 ]
62. f u n c t i o n * g e n 1 ( ) { y i e l d ' a ' ; y i e l d * g e n 2 ( ) ; y i e l d ' c ' ; } f u n c t i o n * g e n 2 ( ) { y i e l d ' b ' ; y i e l d ' c ' ; } [ . . . g e n 1 ( ) ] / / [ ' a ' , ' b ' , ' c ' , ' d ' ]
63. GENERATORS AS OBSERVERS
64. f u n c t i o n * o b s e r v e r ( ) { c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; } l e t c = o b s e r v e r ( ) ; / / n o t e : n o p a r a m t o ` n e x t ( ) ` h e r e o b s e r v e r . n e x t ( ) ;
65. f u n c t i o n * o b s e r v e r ( ) { c o n s o l e . l o g ( ' R e c e i v e d : ' + 1 ) ; c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; } l e t c = o b s e r v e r ( ) ; / / n o t e : n o p a r a m t o ` n e x t ( ) ` h e r e o b s e r v e r . n e x t ( ) ; o b s e r v e r . n e x t ( 1 ) ; / / R e c e i v e d 1
66. f u n c t i o n * o b s e r v e r ( ) { c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; c o n s o l e . l o g ( ' R e c e i v e d : ' + 2 ) ; c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; } l e t c = o b s e r v e r ( ) ; / / n o t e : n o p a r a m t o ` n e x t ( ) ` h e r e o b s e r v e r . n e x t ( ) ; o b s e r v e r . n e x t ( 1 ) ; / / R e c e i v e d 1 o b s e r v e r . n e x t ( 2 ) ; / / R e c e i v e d 2
67. f u n c t i o n * o b s e r v e r ( ) { c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; c o n s o l e . l o g ( ' R e c e i v e d : ' + y i e l d ) ; c o n s o l e . l o g ( ' R e c e i v e d : ' + 3 ) ; } l e t c = o b s e r v e r ( ) ; / / n o t e : n o p a r a m t o ` n e x t ( ) ` h e r e o b s e r v e r . n e x t ( ) ; o b s e r v e r . n e x t ( 1 ) ; / / R e c e i v e d 1 o b s e r v e r . n e x t ( 2 ) ; / / R e c e i v e d 2 o b s e r v e r . n e x t ( 3 ) ; / / R e c e i v e d 3
68. GENERATORS AS COROUTINES
69. f u n c t i o n * f o o ( x ) { v a r y = y i e l d ( x + 1 ) ; v a r z = y i e l d ( y + 1 ) ; r e t u r n ( x + y + z ) ; } l e t i t e r = f o o ( 1 ) ;
70. f u n c t i o n * f o o ( x ) { v a r y = y i e l d ( x + 1 ) ; < - p a u s e v a r z = y i e l d ( y + 1 ) ; r e t u r n ( x + y + z ) ; } l e t i t e r = f o o ( 1 ) ; / / n o t e : n o p a r a m t o ` n e x t ( ) ` h e r e i t e r . n e x t ( ) ; / / { v a l u e : 2 , d o n e : f a l s e }
71. f u n c t i o n * f o o ( x ) { v a r y = 2 ( x + 1 ) ; < - r e s u m e v a r z = y i e l d ( y + 1 ) ; < - p a u s e r e t u r n ( x + y + z ) ; } l e t i t e r = f o o ( 1 ) ; / / n o t e : n o p a r a m t o ` n e x t ( ) ` h e r e i t e r . n e x t ( ) ; / / { v a l u e : 2 , d o n e : f a l s e } i t e r . n e x t ( 2 ) ; / / { v a l u e : 3 , d o n e : f a l s e }
72. f u n c t i o n * f o o ( x ) { v a r y = y i e l d ( x + 1 ) ; v a r z = 3 ( y + 1 ) ; < - r e s u m e r e t u r n ( x + y + z ) ; } l e t i t e r = f o o ( 1 ) ; / / n o t e : n o p a r a m t o ` n e x t ( ) ` h e r e i t e r . n e x t ( ) ; / / { v a l u e : 2 , d o n e : f a l s e } i t e r . n e x t ( 2 ) ; / / { v a l u e : 3 , d o n e : f a l s e } i t e r . n e x t ( 3 ) ; / / { v a l u e : 6 , d o n e : t r u e }
73. GENERATORS FOR ASYNCHRONOUS PROGRAMMING
74. f u n c t i o n r e q ( u r l ) { d o A j a x ( u r l , f u n c t i o n ( r e s p o n s e ) { i t . n e x t ( r e s p o n s e ) ; } ) ; } f u n c t i o n * a s y n c ( ) { l e t r 1 = y i e l d r e q ( ' / r e q 1 ' ) ; l e t r 2 = y i e l d r e q ( ` / r e q 2 ? i d = $ { r 1 . i d } ` ) ; c o n s o l e . l o g ( ` r 2 : $ { r 2 } ` ) ; } v a r i t = a s y n c ( ) ;
75. f u n c t i o n r e q ( u r l ) { d o A j a x ( u r l , f u n c t i o n ( r e s p o n s e ) { i t . n e x t ( r e s p o n s e ) ; } ) ; } f u n c t i o n * a s y n c ( ) { l e t r 1 = y i e l d r e q ( ' / r e q 1 ' ) ; < - p a u s e l e t r 2 = y i e l d r e q ( ` / r e q 2 ? i d = $ { r 1 . i d } ` ) ; c o n s o l e . l o g ( ` r 2 : $ { r 2 } ` ) ; } v a r i t = a s y n c ( ) ; i t . n e x t ( ) ; / / k i c k i t o f f
76. f u n c t i o n r e q ( u r l ) { d o A j a x ( u r l , f u n c t i o n ( r e s p o n s e ) { i t . n e x t ( r e s p o n s e ) ; < - r e s u m e } ) ; } f u n c t i o n * a s y n c ( ) { l e t r 1 = { i d : 1 2 3 } r e q ( ' / r e q 1 ' ) ; l e t r 2 = y i e l d r e q ( ' / r e q 2 ? i d = 1 2 3 ' ) ; < - p a u s e c o n s o l e . l o g ( ` r 2 : $ { r 2 } ` ) ; } v a r i t = a s y n c ( ) ; i t . n e x t ( ) ; / / k i c k i t o f f
77. f u n c t i o n r e q ( u r l ) { d o A j a x ( u r l , f u n c t i o n ( r e s p o n s e ) { i t . n e x t ( r e s p o n s e ) ; < - r e s u m e } ) ; } f u n c t i o n * a s y n c ( ) { l e t r 1 = y i e l d r e q ( ' / r e q 1 ' ) ; l e t r 2 = { a : 1 } r e q ( ` / r e q 2 ? i d = $ { r 1 . i d } ` ) ; c o n s o l e . l o g ( ' r 2 : { a : 1 } ) ; } v a r i t = a s y n c ( ) ; i t . n e x t ( ) ; / / k i c k i t o f f
78. ERROR HANDLING
79. f u n c t i o n r e q ( u r l ) { d o A j a x ( u r l , ( ) = > { } , ( e r r ) = > { i t . t h r o w ( ' r e q f a i l e d ' ) ; } ) ; } f u n c t i o n * a s y n c ( ) { t r y { l e t r 1 = y i e l d r e q ( ' / r e q 1 ' ) ; } c a t c h ( e ) { c o n s o l e . l o g ( e ) ; } } v a r i t = a s y n c ( ) ;
80. f u n c t i o n r e q ( u r l ) { d o A j a x ( u r l , ( ) = > { } , ( e r r ) = > { i t . t h r o w ( ' r e q f a i l e d ' ) ; } ) ; } f u n c t i o n * a s y n c ( ) { t r y { l e t r 1 = y i e l d r e q ( ' / r e q 1 ' ) ; < - p a u s e } c a t c h ( e ) { c o n s o l e . l o g ( e ) ; } } v a r i t = a s y n c ( ) ; i t . n e x t ( ) ; / / k i c k i t o f f
81. f u n c t i o n r e q ( u r l ) { d o A j a x ( u r l , ( ) = > { } , ( e r r ) = > { i t . t h r o w ( ' r e q f a i l e d ' ) ; < - r e s u m e } ) ; } f u n c t i o n * a s y n c ( ) { t r y { l e t r 1 = y i e l d r e q ( ' / r e q 1 ' ) ; } c a t c h ( e ) { c o n s o l e . l o g ( e ) ; / / E r r o r : r e q f a i l e d } } v a r i t = a s y n c ( ) ; i t . n e x t ( ) ; / / k i c k i t o f f
82. RESOURCES - Kyle Simpson - Dr. Axel Rauschmeyer - Nicholas Zakas ECMAScript® 2015 Language Specification YDKJS - ES6 & Beyond Exploring ES6 Understanding ECMAScript 6 Learn ES6 - Babel Kangax compatibility table ES6 Fiddle
83. THANKS! TIM DOHERTY @TimCDoherty timdoherty.net
84. VS. FOR...IN Iterates over property names vs. property values
85. VS. FOREACH() Iteration can be cancelled with `break` statement