Txjs talk

Ecma TC39:The Good,
The Bad, and the Ugly

Saturday, June 11, 2011

Ecma TC39:The Good,
• A Sweaty Standards Saga


Ecma TC39:The Good,

• Third part of a trilogy...


Ecma TC39:The Good,

• Third part of a trilogy...

• Brendan Eich

brendan@mozilla.org


Standards Committees


History


History
• ECMA founded May 1961


History

• ECMA-234 standardized
Windows API, driven by
European governments


History


• Netscape took JS to ECMA
in November 1996
(pictured: Jan van den Beld,
S-G ECMA at the time)


History


• Netscape took JS to ECMA
in November 1996
(pictured: Jan van den Beld,
S-G ECMA at the time)

• Sun failed to repeat w/ Java


The Good


Good Parts


Good Parts
• Expert shooters (@awbjs, crock, erights, @littlecalculist,
@samth, @slightlylate, Waldemar Horwat, many more)


Good Parts

• Care & love for JS as a good in itself, free of biz. agendas


Good Parts


• Consensus-driven -> “intersubjectivity” (Husserl)


Good Parts


• Consensus-driven -> “intersubjectivity” (Husserl)

• "Logic presumes a separation of subject from object;
therefore logic is not ﬁnal wisdom.This is Zen. This is my
motorcycle maintenance. "
— Robert M. Pirsig (Zen and the Art of Motorcycle
Maintenance: An Inquiry Into Values)


The School of Athens


Hermeneutic Cycles


Hermeneutic Cycles
• Language design requires
interpretation: of tradition,
culture, technical specs, also of
one another as subjects among
the TC39 members


Hermeneutic Cycles
the TC39 members

• Interpretation must circle
(Heidegger) or spiral
(Gadamer, Schön)


Hermeneutic Cycles
the TC39 members

• Interpretation must circle
(Heidegger) or spiral
(Gadamer, Schön)

• Global optimization, balance


The Bad


Bad Parts


Bad Parts
• Zero-sum gaming (“cannot have X and independent Y”)


Bad Parts

• Horse-trading like congress-critters (“I give you X, you
give me Y”)


Bad Parts

give me Y”)

• Premature/piece-wise complexity-budget bean-counting.
Risks getting stuck hill-climbing at local maxima (see the
Hermeneutic spiral)


Bad Parts

give me Y”)

• Premature/piece-wise complexity-budget bean-counting.
Risks getting stuck hill-climbing at local maxima (see the
Hermeneutic spiral)

• “Scenario-solving” without decomposition into sound
and orthogonal primitives that work with the rest of the
language (E4X is one example)


The Ugly


Competitive Drive


Competitive Drive
• Meta-discussions that can hide business agendas:


Competitive Drive

• M-d #14: “This language doesn’t really need X”


Competitive Drive


• M-d #39: “This will forever change the way JS is used”


Competitive Drive



• M-d #27: “Won’t this confuse n00bs?”


Competitive Drive




• All valid:YAGNI, don’t-make-it-Java, keep-it-approachable


Competitive Drive





• All meta-endless, without speciﬁc arguments, evidence


Competitive Drive





• All meta-endless, without speciﬁc arguments, evidence

• Better: address concrete use-cases, ﬁll language gaps


Approved for ES.next

mozilla

13



• let, const, function in block scope

mozilla

13




• destructuring: let {x, y} = pt; let [s, v, o] = triple()

mozilla

13





• parameter default values: function f(x, y=1, z=0) {...}

mozilla

13






• rest, spread: function g(i, j, ...r) { return r.slice(i, j); }
let a = [0,1,2,3],
o = new any_constructor(...a)

mozilla

13






let a = [0,1,2,3],

• proxies, weak maps: Proxy.create(handler, proto), new WeakMap

mozilla

13






let a = [0,1,2,3],


• modules: module NewMath { export function fast_sin(x) {...} }

mozilla

13






let a = [0,1,2,3],



• iterators, generators: function* gen() { yield 1; yield 2; }
mozilla

13






let a = [0,1,2,3],



• iterators, generators: function* gen() { yield 1; yield 2; }
mozilla
• comprehensions: return [a+b for (a in A) for (b in B)]

13


Yet more approved for ES.next

mozilla

14



• Binary data:

mozilla

14



• Binary data:

• const Point2D = new StructType({ x: uint32, y: uint32 }),
Color = new StructType({ r: uint8, g: uint8,
b: uint8 }),
Pixel = new StructType({ point: Point2D,
color: Color });

mozilla

14



• Binary data:

b: uint8 }),
color: Color });

• const Triangle = new ArrayType(Pixel, 3);

mozilla

14



• Binary data:

b: uint8 }),
color: Color });

• const Triangle = new ArrayType(Pixel, 3);

• 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 } }]);
mozilla

14


Classes made it (Yay, I think? Why am I sad?)

mozilla

15



• Sugar for prototypal object pattern, also supports closure patterns:

mozilla

15




• class Point {
constructor(x, y) {
private x = x;
private y = y;
public closed_r() { return Math.sqrt(x*x + y*y); }
}
get x() { return @x; }
get y() { return @y; }
equals(p) { return @x === p@x && @y === p@y; }
proto_r() { return Math.sqrt(@x * @x + @y * @y); }
}

mozilla

15




• class Point {
constructor(x, y) {
private x = x;
private y = y;
}
}

• Private member reference syntax (@x, p@x) still up in the air...
mozilla

15




• class Point {
constructor(x, y) {
private x = x;
private y = y;
}
}

• Private member reference syntax (@x, p@x) still up in the air...

• extends, prototype, and super work the way you want
mozilla

15


Private Name objects

mozilla

16



• A built-in module providing unique property naming:

mozilla

16




• module Name = require "@name";

const key = Name.create("secret");

function MyClass(privateData) {
this[key] = privateData;
}
MyClass.prototype = {
doStuff() { ... this[key] ... }
};

mozilla

16




• module Name = require "@name";

const key = Name.create("secret");

function MyClass(privateData) {
this[key] = privateData;
}
MyClass.prototype = {
doStuff() { ... this[key] ... }
};

• No loss of privacy via Proxies: key becomes key.public when passed as id
to a trap; only the keymaster can tell by testing key.public === id
mozilla

16


Quasis

• Injection-safer string interpolation and domain-speciﬁc languages

• Backtick-quoted string desugars to a function call that operates on the literal
portions and substitution results:

• quasi`literalPart1${substitution}literalPart2` desugars to

• quasi({raw: ["literalPart1", "literalPart1"],
unescaped: ["literalPart1", "literalPart1"]},
substitution)

• Multiline string literals w/o preﬁx: `literalPart1${substitution}
(yes, that was a newline!) literalPart2`
mozilla
• Multiline regexp literals: re`literalPart1${substitution}
(yes, that was a newline!) w+ literalPart2`
17


Harmony


Harmony
• Yes, we are a commitee


Harmony

• We try to avoid design by committee by


Harmony


• De-facto standards codiﬁcation


Harmony



• The “Champions” model


Harmony




• Developers matter to browser vendors more than ever


Harmony




• Developers matter to browser vendors more than ever

• Make your voices heard with cogent arguments (avoid
rehashing, no trolling: es-discuss@mozilla.org)


Languages are like
friends (and enemies)


Languages are like
• Package deal: bad parts along with good


Languages are like

• You can subset


Languages are like

• You can subset

• You do sometimes debug your friends


Languages are like

• You can subset


• You can unfriend, betray, change alliances


Languages are like

• You can subset


• You can unfriend, betray, change alliances

• JS wants to remain your BFF!


Stand-off / Q&A


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