So bright it burns - Speaker Deck

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THE FUTURE OF JAVASCRIPT SO BRIGHT IT BURNS

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Hi, I’m dherman @littlecalculist

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I — JavaScript and I love the language it almost is...

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tl;dr

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TIER 1 AWESOMENESS modules • block scoping • generators • proxies • binary data • destructuring • rest-args & defaults TIER 2 AWESOMENESS name objects • custom iteration • comprehensions • string templates • hash tables & weak maps

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Great languages deserve great libraries and that means modules

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browser

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var Collections = (function() { function Dict() { ... } return { Dict: Dict }; })();

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“The human compiler, at work.” — Paul Graham “The sincerest form of feature request.” — someone?

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module Collections { export function Dict() { ... } }

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import { $ } from "jquery.js"; import { map, each } from "underscore.js";

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import { $ } from "jquery.js"; import { map, each } from "underscore.js"; loaded once, before execution

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let is the new var block scoping (at long, long last)

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for (i = 0; i < a.length; i++) { var x = a[i]; x.onclick = function() { x.toggle() }; }

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for (i = 0; i < a.length; i++) { let x = a[i]; x.onclick = function() { x.toggle() }; }

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Generator functions an alternative to callback spaghetti

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function* counter() { yield 1; yield 2; yield 3; } var g = counter(); alert(g.next()); // 1 alert(g.next()); // 2 alert(g.next()); // 3

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XHR("foo.txt", function(foo) { XHR("bar.txt", function(bar) { XHR("baz.txt", function(baz) { setTimeout(function() { status.innerHTML = foo + bar + baz; }, 1000); }); }); });

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XHR("foo.txt", function(foo) { XHR("bar.txt", function(bar) { XHR("baz.txt", function(baz) { setTimeout(function() { status.innerHTML = foo + bar + baz; }, 1000); }); }); }); pyramid of doom

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Pour 1/2 cup water into pan. When you’re done: Bring water to boil. When that’s done: Lower heat and add rice. After 15 minutes: Turn off heat and serve.

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spawn(function*() { var foo = yield read("foo.txt"), bar = yield read("bar.txt"), baz = yield read("baz.txt"); yield sleep(1000); status.innerHTML = foo + bar + baz; });

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Proxies meta-programming for fun and profit

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var p = new Proxy(obj, { get: function(...) { ... }, set: function(...) { ... }, delete: function(...) { ... }, ... });

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Bits, bytes and blobs binary file and network I/O

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var Point2D = new StructType({ x: uint32, y: uint32 }); var Color = new StructType({ r: uint8, g: uint8, b: uint8 });

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var Pixel = new StructType({ point: Point2D, color: Color }); var Triangle = new ArrayType(Pixel, 3);

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new Triangle([ { point: { x: 0, y: 0 }, color: { r: 255, g: 255, b: 255 } }, { point: { x: 5, y: 5 }, color: { r: 128, g: 0, b: 0 } }, { point: { x: 10, y: 0 }, color: { r: 0, g: 0, b: 128 } } ])

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Destructuring try it, you’ll like it

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var { r, g, b } = thing.color; var [x, y] = circle.center; [a, b] = [b, a];

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function div({ width, height, border }) { ... }

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Rest-args and defaults death to the arguments object!

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function f(i, j, ...rest) { return rest.slice(i, j); }

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array.push(thing1, thing2, ...moarThings); var shape = new Shape(...points);

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function img(src, width=320, height=240) { ... }

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function img({ src, width=320, height=240 }) { ... }

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Name objects first-class, unique property keys

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function Container() { var secret = 3; this.service = function() { if (secret-‐-‐) { ... } }; }

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var key = Name.create("secret"); function Container() { this[key] = 3 } Container.prototype = { service: function() { if (this[key]-‐-‐) { ... } } };

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Custom object iteration taming the for-in loop

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for (x in [3, 4, 5]) // 0, 1, 2 (d’oh) for (x of [3, 4, 5]) // 3, 4, 5 for (x of keys(o)) // keys in o for (x of values(o)) // values of o for ([k, v] of items(o)) // props of o

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import iterate from "@iter"; obj[iterate] = function() { return { next: function() { ... } } } for (x of obj) { ... }

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Comprehensions beautiful array processing

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[ x * y for (x of obj1) for (y of obj2) ] ( x * y for (x of obj1) for (y of obj2) )

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String templates untangling string formatting code

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\nohai, " + firstName + " " + lastName + "\n

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ohai, ${firstName} ${lastName}

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safeHTML`

ohai, ${firstName} ${lastName}

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Object-keyed tables hash tables and weak maps

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var scores = new Map(); var player1 = { ... }; scores.set(player1, 0); scores.get(player1) // 0

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var markers = new WeakMap(); var tile = new Tile(...); var results = [...]; tiles.set(tile, results);

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There is a bigger picture.

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“Be a better language for: a. complex apps b. libraries c. code generators”

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Motivated by use cases. Solve with simple, general, composable features. Pieces have to fit together in a cohesive whole.

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study the issues study the big picture study the issues again study the big picture again study the issues again SHIP IT!

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Work in the open wiki.ecmascript.org es-discuss

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How soon is now?

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We (Ecma) are working hard and fast on the spec. We (vendors) are prototyping and shipping features now. Transpilers as language shims: Traceur, Narcissus

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