ES6: the future is now

4cf764dcd5d1efc1de7051603bdf8215?s=47 JSIST
September 28, 2014

ES6: the future is now

JSIST 2014
By : Sebastiano Armeli
http://jsist.org

4cf764dcd5d1efc1de7051603bdf8215?s=128

JSIST

September 28, 2014
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  1. Sebastiano Armeli @sebarmeli http://html5hub.com/wp-content/uploads/2013/11/es6-hiway-sign.png

  2. @sebarmeli Sebastiano Armeli

  3. ES6

  4. History 1995 1996 1997 1998 1999 2000 2003 (May) B.

    Eich invented Mocha (Dec) LiveScript renamed to JavaScript JSScript (June) ECMA-262 Ed.1! ! by TC39 committee ECMA-262 Ed.2 ECMA-262 Ed.3 ECMA-262 Ed.4 started ECMA-262 Ed.4 abandoned (Sep) Mocha renamed to LiveScript
  5. History 2005 2007 2008 2009 2011 2014 2015 ES 4

    again! (Adobe, Mozilla,! Google)! ES 3.1 ! (Microsoft, Yahoo)! beginning ES 5 spec finalized (June) ECMA-262 Ed.5 (Dec) ES 6 spec completion (Mar) Start publication! (Jun) ECMA-262 Ed.6 ! target release (July) Agreement:! ES3.1 & ES-Harmony! ! ES3.1 becomes ES5
  6. ECMA-262 TC39 ES 4 ES-Harmony ES.Next ES 6 ECMA ES

    7 es-discuss
  7. Iteration & Generators Summary Arrow Functions Collections Modularity / Classes

    / Templates Scoping / Destructing / Parameters API improvements Proxies
  8. Iteration & Generators Summary Collections Modularity / Classes / Templates

    Scoping / Destructing / Parameters API improvements Proxies Arrow Functions
  9. (Fat) arrow function var y = (x) => x +

    1 var y = function(x) { return x + 1; } ES6 ES5
  10. (Fat) arrow function var y = function(x) { return x

    + 1; } ES6 ES5 Syntax sugar var y = (x) => x + 1
  11. (Fat) arrow function var y = function(x) { return x

    + 1; } ES6 ES5 Syntax sugar Lexical `this` binding var y = (x) => x + 1
  12. (Fat) arrow function var y = function(x) { return x

    + 1; } ES6 ES5 No constructor Syntax sugar Lexical `this` binding var y = (x) => x + 1
  13. var y = (x) => {return x + 1} var

    y = function(x) { return x + 1; } ES6 ES5
  14. var y = (x) => {return x + 1} var

    y = function(x) { return x + 1; } var z = (x, y) => ({ x: x, y: y }) var z = function(x, y) { return { x: x, y: y }; } ES6 ES5
  15. var mapFn = words => words.map((w) => w.length); var mapFn

    = function(words) { return words.map(function(w) { return w.length; } } ES6 ES5 mapFn([‘sea’, ‘beach’, ‘do’]); // [3,5,2]
  16. var obj = { doIt: function(){}, handle: function(){ var that

    = this; document.addEventListener(‘click’, function(e) { that.doIt(); }); } } ES3
  17. var obj = { doIt: function(){}, handle: function(){ document.addEventListener(‘click’, function(e)

    { this.doIt(); }.bind(this)); } } ES5 var obj = { doIt: function(){}, handle: function(){ var that = this; document.addEventListener(‘click’, function(e) { that.doIt(); }); } } ES3
  18. var obj = { doIt: function(){}, handle: function(){ document.addEventListener(‘click’, (e)

    => this.doIt()); } } ES6
  19. Object.getPrototypeOf(() => {})

  20. Object.getPrototypeOf(() => {}) Function.prototype

  21. When to use ‘function’ ?

  22. Constructors Generators (Methods in object literals)

  23. Summary Arrow Functions Collections API improvements Proxies Scoping / Destructing

    / Parameters Iteration & Generators Modularity / Classes / Templates
  24. Block Scoping Each BLOCK has got its lexical environment let/const

    bind variables to the lexical environment Variables declared with let/const are NOT hoisted
  25. var vs let (function() { console.log(y) // “undefined” if (true)

    { var y = “value”; } console.log(y) // “value” }());
  26. var vs let (function() { if (true) { let y

    = “value”; } console.log(y) // ERROR!! }()); (function() { console.log(y) // “undefined” if (true) { var y = “value”; } console.log(y) // “value” }());
  27. const (function() { const X; X = “foo”; // ERROR:

    x unitialized }()); (function() { const X = “foo”; X = “foo2”; // ERROR: x is read-only }());
  28. Block functions if (true) { function fn () {} }

    ! fn(); // ERROR!
  29. Destructing array var [x,y] = [‘a’, ‘b’]; ! console.log(x); //

    ‘a’ ! console.log(y); // ‘b’ ! ! var [x,y] = [y, x]; ! console.log(x); // ‘b’
  30. Destructing object var obj = {width: 50, height: 100}; !

    ! var {width: w, height: h} = obj; var {width, height} = obj; ! ! console.log(width); // 50 console.log(w); // 50 console.log(height); // 100 console.log(h); // 100
  31. Multiple return value var fn = function(){ return [“50”, “100”];

    } ! var [width, height] = fn(); ! console.log(width); //50 console.log(height); //100
  32. var fn = function(){ return { foo: “bar”, fizz: “buzz”

    } } ! var {foo, fizz} = fn(); ! console.log(foo); //“bar” console.log(fizz); //“buzz”
  33. Parameter default values function(foo) { foo = foo || “a”;

    }
  34. function(foo) { foo = foo || “a”; } function(foo =

    “a”) {} Parameter default values
  35. function fn(…args) { console.log(args); //[“a”, “b”, “c”] args.forEach(function(arg) { console.log(arg);

    }); } ! fn(“a”, “b”, “c”); ! // a // b // c Rest parameters
  36. Rest parameters function fn(a, …args) { console.log(args); //[“b”, “c”] args.forEach(function(arg)

    { console.log(arg); }); } ! fn(“a”, “b”, “c”); ! // b // c
  37. Spread operator function fn(a, b, c) {} ! var array

    = [“A”, “B”, “C”]; fn.apply(null, array);
  38. function fn(a, b, c) {} ! var array = [“A”,

    “B”, “C”]; fn.apply(null, array); fn(…array); Spread operator
  39. function fn({id, name}) { console.log(name); } ! fn({name: “Seb”}); //

    “Seb Named parameters
  40. Iteration & Generators Summary Collections API improvements Proxies Arrow Functions

    Scoping / Destructing / Parameters Modularity / Classes / Templates
  41. for-of for-of loop on ‘iterables’ and iterators Arrays/Sets/Maps are ’iterables’

    for-in limitations
  42. for-of var array = [“a”, “b”, “c”]; ! for (let

    el of array) { console.log(el); } ! // “a” // “b” // “c”
  43. Iterable { @@iterator: function() -> iterator } { next: function()

    -> any } Iterators
  44. Iterator var array = [“a”, “b”, “c”]; ! array.entries() //

    Array Iterator array.keys() // Array Iterator Iterator from Array, Map, Set
  45. function* g() { yield “a”; yield “b”; } Generator var

    generator = g(); generator ‘constructor’ generator.next(); //{ value: “a”, done: false} generator.next(); //{ value: “b”, done: false} generator.next(); //{ value: undefined, done: true}
  46. ! function* g() { yield “a”; var retVal = yield

    “b”; return retVal; } var generator = g(); generator.next().value; //“a” generator.next().value; //“b” generator.next(“c”).value; //“c”
  47. ! function* asyncFn() { var data = yield getUser(); doSomethingElse(data);

    } function run(genFunction) { var generator = genFunction(); generator.next().value.then(function(val){ generator.next(val); }, function(err) { generator.throw(err); }); } run(asyncFn); Promise
  48. for (let el of generator) { console.log(el); } Generators are

    iterables
  49. Iteration & Generators Summary Collections API improvements Proxies Arrow Functions

    Scoping / Destructing / Parameters Modularity / Classes / Templates
  50. Set NO duplicates values

  51. Set NO duplicates values Different types in a set

  52. Set NO duplicates values Different types in a set add(key)/

    has(key) / delete(key)
  53. Set NO duplicates values Different types in a set add(key)/

    has(key) / delete(key) values() -> Iterator
  54. let countries = new Set(); countries.add(“US”); countries.add(“Italy”); countries.add(“US”); ! countries

    // Set [“US”, “Italy”]
  55. let countries = new Set([“US”, “Italy”]); countries // Set [“US”,

    “Italy”] ! ! ! countries.delete(“Italy”); countries // Set [“US”]
  56. ! for(let country of countries.values()) { console.log(country); // “US” }

    ! for(let country of countries) { console.log(country); // “US” }
  57. Map {“foo” : “bar” }

  58. Map {“foo” : “bar” } Keys can be objects

  59. Map {“foo” : “bar” } Keys can be objects get(key);

    has(key); set(key,val)
  60. Map {“foo” : “bar” } get(key); has(key); set(key,val) delete(key); clear();

    forEach(); Keys can be objects
  61. let dict = new Map(); dict.set(“A”, 1); dict.set(“B”, 2); !

    dict // Map {“A”: 1, “B”: 2}
  62. let dict = new Map(); dict.set(“A”, 1); dict.set(“B”, 2); !

    dict // Map {“A”: 1, “B”: 2} ! dict.get(“A”); // “1” dict.delete(“B”);
  63. for(let w of dict.keys()) { // Map Iterator console.log(w); //

    “A” } ! for(let w of dict.values()) { // Map Iterator console.log(w); // 1 } ! dict.clear(); dict.size; // 0
  64. let dict = new Map([[“x”, 1], [“y”, 2]]); ! !

    dict; // Map {x: 1, y: 2} ! ! ! for(let w of dict) { ! console.log(w); // [“x”, 1] // [“y”, 2] ! });
  65. dict.forEach(function(val, key, map) { ! console.log(val); // x // y

    ! console.log(key); // 1 // 2 ! console.log(map); // Map { x: 1, y: 2} ! });
  66. WeakMap Avoid memory leaks

  67. WeakMap Avoid memory leaks Reference to the key obj held

    weakly
  68. WeakMap Avoid memory leaks Reference to the key obj held

    weakly Keys must be an objects
  69. WeakMap Avoid memory leaks Reference to the key obj held

    weakly Keys must be an objects No iterators methods
  70. Object properties ! with ! Map / WeakMap

  71. Summary Collections API improvements Proxies Arrow Functions Scoping / Destructing

    / Parameters Iteration & Generators Modularity / Classes / Templates
  72. Object Literal ! let obj = { ! __proto__: parentObj,

    meth1(a,b) { ! } ! };
  73. Module ! export function register(ad) { return ad; } !

    import {register} from “ads”; var app = { doIt: function() { register({}); } } export app; app.js lib/ads.js
  74. export default class {}; // Ad.js import Ad from ‘ad';

    // app.'s ! ! import { meth as method } from ‘a’;
  75. Class ! class Animal { constructor(name) { this.name = name;

    } toString() { return “This is: ” + this.name; } }
  76. Subclass - super ! class Cat extends Animal { constructor(name,

    ownerName) { super(name); this.ownerName = ownerName; } ! toString() { return super() + “ owned by ” + this.ownerName; } }
  77. ! class Animal { constructor(name) { this.name = name; }

    toString() { return “This is: ” + this.name; } } class Cat extends Animal { constructor(name, ownerName) { super.constructor(name); this.ownerName = ownerName; } ! toString() { return super.toString() + “ owned by ” + this.ownerName; } }
  78. ! function Animal(name) { this.name = name; } ! Animal.prototype.toString

    = function() { return “This is: ” + this.name; }; ! function Cat(name, ownerName) { Animal.call(this, name); this.ownerName = ownerName; } ! Cat.prototype = Object.create(Animal.prototype); Cat.prototype.constructor = Cat; Cat.prototype.parent = Animal; ! Cat.prototype.toString = function() { var super = Animal.prototype.toString.call(this); return super + “ owned by ” + this.ownerName; };
  79. Template strings var a = “hello”; var b = “world”;

    ! `${a} ${b}!`
  80. Template strings var a = “hello”; var b = “world”;

    ! `${a} ${b}!` var multiline = `Hello world !!!`;
  81. Summary Collections API improvements Proxies Arrow Functions Scoping / Destructing

    / Parameters Iteration & Generators Modularity / Classes / Templates
  82. String methods String.prototype.startsWith(str) => boolean String.prototype.endsWith(str) => boolean String.prototype.contains(str) =>

    boolean String.prototype.repeat(num) => string
  83. Number methods Number.isInteger(num) => boolean Number.isNaN(num) => boolean Number.isFinite(num) =>

    boolean …
  84. Array methods Array.from(obj) => Array Array.prototype.entries => Iterator Array.of(…args) =>

    Array Array.prototype.keys => Iterator Array.prototype.values => Iterator
  85. var divs = document.querySelectorAll("div"); ! Array.from(divs); ! // [<div></div>, </div></div>]

    ! Array.of(10, 11); ! // [10, 11] !
  86. var array = [“a”, “b”, “c”]; ! for (let [index,

    el] of array.entries()) { console.log(index, el); // 0 “a” // 1 “b” // 2 “c” } ! for (let index of array.keys()) { console.log(index); } ! for (let el of array.values()) { console.log(el); } !
  87. Object methods Object.setPrototypeOf(obj, proto) Object.assign(obj, mixin) Object.is(value1, value2)

  88. Math methods Math.log2(num) => num Math.log10(num) => num Math.sinh(num) =>

    num Math.cosh(num) => num …
  89. Summary Collections API improvements Proxies Arrow Functions Scoping / Destructing

    / Parameters Iteration & Generators Modularity / Classes / Templates
  90. Proxies Proxy(targetObject, interceptors) ! Different use cases (logging, mocking) Meta-programming

  91. var obj = {num: 1}; ! obj = new Proxy(obj,

    { set: function (target, property, value) { target[property] = value + 1; } }); ! obj.num = 2 // [[Set]] console.log(obj.num); // 3 Proxies
  92. function createDefensiveObject(target) { return new Proxy(target, { get: function(target, property)

    { if (property in target) { return target[property]; } else { throw new ReferenceError(); } } }); } ! var obj = createDefensiveObject({name: “Seb”}); console.log(obj.lastname); //ReferenceError http://www.nczonline.net/blog/2014/04/22/creating-defensive-objects-with-es6-proxies/ Proxies
  93. Iteration & Generators Recap Arrow Functions Collections Scoping / Destructing

    / Parameters API improvements Proxies Modularity / Classes / Templates
  94. Promises Symbols Better Unicode support Optimized tail calls Other Features..

  95. ES6 today Traceur compiler (Google) es6-transpiler es6-module-transpiler (Square) es6-shim defs.js

  96. http://wiki.ecmascript.org https://people.mozilla.org/~jorendorff/es6-draft.html http://kangax.github.io/compat-table/es6/ http://esdiscuss.org/ @sebarmeli Sebastiano Armeli