Mozilla's NodeConf talk

SpiderNode, V8Monkey, and You

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Thursday, May 5, 2011

What?

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What?

In which we put a v8 API on top of spidermonkey without futzing with a separate build
system. Prep work for spidernode. (from an autoupdated unofﬁcial mozilla-central clone)

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Why?

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Why?

• We at Mozilla <3 V8 (we <3 WebKit/JavaScriptCore too; Chakra not so much)

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Why?


• SpiderMonkey (born 1996, reborn 2008 [TraceMonkey], 2010 [JaegerMonkey],
2011 [TypeInferenceMonkey], 2012 [IonMonkey] -- “My afterlife is *so* boring!” -
Heathers) really needs a better API

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Why?



• V8 has a nice “C++ the good parts” API

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Why?




• Template types, RAII storage class auto helpers, GC all the way down

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Why?





• JS the language is evolving -- Harmony coming in ES.next

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Why?





• JS the language is evolving -- Harmony coming in ES.next

• Node is a great testbed for new JS features
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Approved for ES.next

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• let, const, function in block scope

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

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

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

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

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

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


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

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



• iterators, generators: function* gen() { yield 1; yield 2; }
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let a = [0,1,2,3],



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

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Yet more approved for ES.next

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• Binary data:

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• 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 });

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• Binary data:

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

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

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• 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 } }]);
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Hot, but not yet in Harmony

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• Arrow function syntax, instead of λ, ƒ, or # (want to save # for later)

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• Just like CoffeeScript: let identity = (x) -> x

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• Expression body: const square = (x) -> (x * x)

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• Statement body: let countUsed = (str) -> {
if (str in usedWords)
usedWords[str]++;
else
usedWords[str] = 1;
}

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usedWords[str]++;
else
usedWords[str] = 1;
}

• Fat arrow too: callback = (msg) => ( this.vmail.push(msg) )

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usedWords[str]++;
else
usedWords[str] = 1;
}

• Fat arrow too: callback = (msg) => ( this.vmail.push(msg) )

• Binding forms: let f() -> “writable”
const K() -> “readonly” mozilla

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What else?

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What else?

• CoffeeScript classes, for prototypal inheritance sugar

• Or a different classes as closure pattern sugar proposal?

• Or (and this is somewhat Coffee-like) extended object initialisers?

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What else?




• Coffee’s @foo for this.foo

• Or some private names or “soft ﬁelds” @ usage?

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What else?






• Paren-free syntax: if x > y return x
while i < n { a.push(i++); }

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What else?






• Paren-free syntax: if x > y return x
while i < n { a.push(i++); }

• More operators: ?? ??= div mod divmod is isnt
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Demo: generators for callback-free i/o

• https://github.com/dherman/taskjs

var {task} = require('./taskjs/lib/task.js');
var fs = require('fs');
function readFile(path) {
return new NodeReadFile(path);
}
function NodeReadFile(path) {
this.path = path;
var wait = this;
fs.readFile(path, function (err, data) {
if (err) {
wait.throw(err);
} else {
wait.return(data);
}

}
}); mozilla

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Demo: generators, continued

• NodeReadFile.prototype = new task.Wait();

task.spawn(function () {
try {
var data = yield readFile('gen.js');
console.log(data.toString('ascii'));
} catch (e) {
console.log(e);
}
});

• You have to write yield a bit (don’t forget it!)

• But you don’t have to write function(){...} nests

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Even shorter generator anti-nesting demo

• let {Wait, spawn, choose} = require('./taskjs/lib/task.js').task;
let newRequest = new Wait();
require('http').createServer(function (req, res) {
newRequest.return([req, res]);
}).listen(10337, "127.0.0.1");
spawn(function () {
let i = 0;
while (true) {
let [req, res] = yield newRequest;
if (req.url === '/') {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello World: ' + i + 'n');
i++;
}
}
}) mozilla
console.log('Server running at http://127.0.0.1:10337/');

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Thanks, contact, more demos, Q&A

• Thanks to @robarnold @sdwilsh @zpao @john_h_ford and @andreasgal

• irc.mozilla.org #spidernode

• spidernode@mozilla.org (mailman subscribe request)

• More demos

• NodeChat running at SSID spidernode 169.254.64.209

• Questions?

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