ES6 Deep Dive

Transcript

1. Dave Herman ES6 Deep Dive Symbols, Structs, Generators

2. None

3. About me • @littlecalculist • http://calculist.org • http://github.com/dherman • Mozilla

   Research • TC39 • Also…

4. In print this December http://effectivejs.com

5. Symbols

6. JS property names are strings var obj = { foo:

   42 }; obj["foo"]; // 42

7. The all-powerful _ character function Dict() { this._entries = {};

   } Don’t touch me, I’m private!

8. When you mean business… __proto__ private SO PRIVATE REALLY GUYS

   SOOO TOTALLY PRIVATE private!

9. Conventions are no guarantee function SuperClass() { this._data = "superclass

   private data"; } function SubClass() { SuperClass.call(this); this._data = "subclass private data"; // collision! } SubClass.prototype = Object.create(SuperClass.prototype);

10. Closures for information hiding function SuperClass() { var data =

    "private data"; this.method = function() { /* ... */ data /* ... */ }; } no sharing: one method per instance!

11. Introducing symbols

12. Introducing symbols var sym = new Symbol("data");

13. Introducing symbols var sym = new Symbol("data"); function SuperClass() {

    this[sym] = "private data"; }

14. Introducing symbols var sym = new Symbol("data"); function SuperClass() {

    this[sym] = "private data"; } SuperClass.prototype.method = function() { /* ... */ this[sym] /* ... */ };

15. Introducing symbols var obj = new SuperClass(); "data" in obj;

    // false "_data" in obj; // false sym in obj; // true

16. Performance • Engines already do string interning • Convertible to

    a fixed offset with inline caches

17. Proposal: scoped symbols private @sym; function SuperClass() { this.@sym =

    "private data"; } SuperClass.prototype.method = function() { /* ... */ this.@sym /* ... */ };

18. Structured binary data

19. Typed arrays var a = new Uint32Array(1024); a[17] = 42;

20. Typed arrays var vertices = new Float32Array([ -1.0, -1.0, 0.0,

    // vertex 1 0.0, 1.0, 0.0, // vertex 2 1.0, -1.0, 0.0 // vertex 3 ]); -1.0 -1.0 0.0 0.0 1.0 0.0 1.0 -1.0 0.0 0 4 8 12 16 20 24 28 32

21. Structs var Point = struct({ x: float32, y: float32, z:

    float32 }); var origin = new Point(0.0, 0.0, 0.0); origin.x; // 0.0 origin.y; // 0.0

22. Arrays of structs var vertices = new Point.array([ { x:

    -1.0, y: -1.0, z: 0.0 }, { x: 0.0, y: 1.0, z: 0.0 }, { x: 1.0, y: -1.0, z: 0.0 } ]); -1.0 -1.0 0.0 0.0 1.0 0.0 1.0 -1.0 0.0 0 4 8 12 16 20 24 28 32

23. JIT compilers — types

24. Applications of structs • WebGL data • File and network

    I/O • Compiling other languages to JS

25. Generators

26. Lies, lies, lies “JS doesn’t have concurrency.” “JS is single-threaded

    so it can’t have race conditions.” “Event-based programming is easy.”

27. Download three files load("foo", function(foo) { load("bar", function(bar) { //

    why wait? load("baz", function(baz) { use([foo, bar, baz]); }); }); });

28. Download three files load("foo", function(foo) { load("bar", function(bar) { //

    why wait? load("baz", function(baz) { use([foo, bar, baz]); }); }); });

29. Download three files var files = []; ["foo", "bar", "baz"].forEach(function(url,

    i) { load(url, function(file) { files.push(file); // no! if (i === 3) // no! use(files); }); });

30. Download three files var files = []; ["foo", "bar", "baz"].forEach(function(url,

    i) { load(url, function(file) { files[i] = file; if (files.length === 3) // still no! use(files); }); });

31. Download three files var files = [], count = 0;

    ["foo", "bar", "baz"].forEach(function(url, i) { load(url, function(file) { files[i] = file; if (++count === 3) use(files); }); });

32. JavaScript is concurrent Cooperative concurrency: easier, but not easy! Handlers

    run sequentially but start concurrently. Shared state 㱺 race conditions 㱺 pain and suffering

33. task.js: Beautiful concurrency spawn(function*() { var files = yield join(load("foo"),

    load("bar"), load("baz")); use(files); }); http://taskjs.org

34. task.js: Beautiful concurrency spawn(function*() { var files = yield join(load("foo"),

    load("bar"), load("baz")); use(files); }); create a task that can be paused pause! http://taskjs.org

35. Generator functions function* evenNumbers() { for (var next = 0;

    true; next += 2) { yield next; } }

36. Generator functions function* evenNumbers() { for (var next = 0;

    true; next += 2) { yield next; } }

37. Generator functions function* evenNumbers() { for (var next = 0;

    true; next += 2) { yield next; } } evenNumbers(); ✗

38. Generator functions function* evenNumbers() { for (var next = 0;

    true; next += 2) { yield next; } } evenNumbers(); ✗

39. Generators function* f() { }

40. Generators function* f() { } .next: var g = f();

    ⋮

41. Generators function* evenNumbers() { /* ... */ } var g

    = evenNumbers(); g.next(); // 0 g.next(); // 2 g.next(); // 4 starts out paused

42. Lazy iteration Dict.prototype.keys = function*() { for (var key in

    this._entries) yield key; };

43. Iterators work with for-of var dict = new Dict(); //

    ... for (var key of dict.keys()) { console.log(key + ": " + dict.get(key)); }

44. Pausing is powerful load("config.json", function(config) { db.lookup(JSON.parse(config).table, username, function(user) {

    load(user.id + ".png", function(avatar) { // ... }); }); });

45. Pausing is powerful load("config.json", function(config) { db.lookup(JSON.parse(config).table, username, function(user) {

    load(user.id + ".png", function(avatar) { // ... }); }); }); later later later

46. Pausing is powerful load("config.json", function(config) { db.lookup(JSON.parse(config).table, username, function(user) {

    load(user.id + ".png", function(avatar) { // ... }); }); }); later later later

47. Pausing with promises load("config.json") .then(function(config) { return db.lookup(JSON.parse(config).table); }) .then(function(user)

    { return load(user.id + ".png"); }) .then(function(avatar) { /* ... */ });

48. Pausing with promises load("config.json") .then(function(config) { return db.lookup(JSON.parse(config).table); }) .then(function(user)

    { return load(user.id + ".png"); }) .then(function(avatar) { /* ... */ });

49. Pausing with promises load("config.json") .then(function(config) { return db.lookup(JSON.parse(config).table); }) .then(function(user)

    { return load(user.id + ".png"); }) .then(function(avatar) { /* ... */ });

50. Pausing with promises load("config.json") .then(function(config) { return db.lookup(JSON.parse(config).table); }) .then(function(user)

    { return load(user.id + ".png"); }) .then(function(avatar) { /* ... */ });

51. Pausing with promises load("config.json") .then(function(config) { return db.lookup(JSON.parse(config).table); }) .then(function(user)

    { return load(user.id + ".png"); }) .then(function(avatar) { /* ... */ });

52. Pausing with promises load("config.json") .then(function(config) { return db.lookup(JSON.parse(config).table); }) .then(function(user)

    { return load(user.id + ".png"); }) .then(function(avatar) { /* ... */ });

53. Tasks yield promises spawn(function*() { var config = JSON.parse(yield load("config.json"));

    var user = yield db.lookup(config.table, username); var avatar = yield load(user.id + ".png"); // ... });

54. Tasks yield promises spawn(function*() { var config = JSON.parse(yield load("config.json"));

    var user = yield db.lookup(config.table, username); var avatar = yield load(user.id + ".png"); // ... });

55. Tasks yield promises spawn(function*() { var config = JSON.parse(yield load("config.json"));

    var user = yield db.lookup(config.table, username); var avatar = yield load(user.id + ".png"); // ... }); looks like a synchronous API!

56. What about errors? load("foo", function(foo) { load("bar", function(bar) { load("baz",

    function(baz) { use([foo, bar, baz]); }, function(err) { /* ... */ }); }, function(err) { /* ... */ }); }, function(err) { /* ... */ });

57. What about errors? load("foo", function(err, foo) { if (err) return

    onError(err); load("bar", function(err, bar) { if (err) return onError(err); load("baz", function(err, baz) { if (err) return onError(err); use([foo, bar, baz]); }); }); });

58. Error handling with promises var p = load("config.json") .then(function(config) {

    /* ... */ } .then(function(user) { /* ... */ }) .then(function(avatar) { /* ... */ }); when(p, function(result) { /* ... */ }, function(err) { /* ... */ });

59. Error handling with tasks spawn(function*() { try { var config

    = JSON.parse(yield load("config.json")); var user = yield db.lookup(config.table, username); var avatar = yield load(user.id + ".png"); // ... } catch (e) { /* ... */ } });

60. Wait for multiple events spawn(function*() { var [foo, bar, baz]

    = yield join(load("foo"), load("bar"), load("baz")); // ... });

61. Purposefully race events spawn(function*() { try { var foo =

    yield select(load("foo"), timeout(3000)); // ... } catch (e) { /* timed out */ } });

62. Generators • Interruptible computations 㱺 custom iterators • Pausing with

    yield 㱺 concurrency minus the callbacks

63. Something completely different

64. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]]

65. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]]

66. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]] "[object Object]"

67. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]] "[object Object]"

68. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]] "[object Object]" true true true

69. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]] "[object Object]" 3

70. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]] "j"

71. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]] "false" "j"

72. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]] "false" 3 "j"

73. ({}+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]] "j" "s"

74. ! + { } [ ] ( ) \n ===

    JavaScript

75. Um. So… why?

76. • No reason. Um. So… why?

77. • Yosuke Hasegawa: JSF*ck • Patricio Palladino: Hieroglyphy • Me:

    pure JS, no browser API’s Not the first deranged weirdo

78. > String+[] "function String() { [native code] }" "S"

79. > "".constructor+[] "function String() { [native code] }" "S"

80. > ""["constructor"]+[] "function String() { [native code] }" "S"

81. > [].slice.call(""["constructor"]+[]) ["f","u","n","c","t","i","o","n"," ","S","t","r", /* ... */] "S"

82. > [].slice.call(""["constructor"]+[]) [" ","f","u","n","c","t","i","o","n"," ","S","t","r", /* ... */] "S"

83. > function nonWhitespace(s) { return !/^\s*$/.test(s) } > [].slice.call(""["constructor"]+[]).filter(nonWhitespace) ["f","u","n","c","t","i","o","n","S","t","r",

    /* ... */] "S"

84. > Number("f") NaN > Number(" ") 0 > isNaN("f") true

    > isNaN(" ") false "S"

85. > [].slice.call(""["constructor"]+[]).filter(isNaN) ["f","u","n","c","t","i","o","n","S","t","r", /* ... */] "S"

86. > [].slice.call(""["constructor"]+[]) .filter(Function("return isNaN")()) ["f","u","n","c","t","i","o","n","S","t","r", /* ... */] "S"

87. > [].slice.call(""["constructor"]+[]) .filter(Array.constructor("return isNaN")()) ["f","u","n","c","t","i","o","n","S","t","r", /* ... */] "S"

88. > [].slice.call(""["constructor"]+[]) .filter([].constructor.constructor("return isNaN")()) ["f","u","n","c","t","i","o","n","S","t","r", /* ... */] "S"

89. > [].slice.call(""["constructor"]+[]) .filter([].constructor.constructor("return isNaN")())[8] "S" "S"

90. > (9).toString() "9" > (15).toString(16) "f" > (16).toString(17) "g" "p"

91. > (25).toString(26) "p" "p"

92. > (25)["toString"](26) "p" "p"

93. > escape(" ") "%20" "%"

94. > Function("return escape")()(" ") "%20" "%"

95. > Function("return escape")()(" ")[0] "%" "%"

96. > Function("return unescape")()("%3b") ";" Any ASCII character

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