gsathya

➜  v8 git:(69191fe7d6) eshost -t _test.js
┌────────────────┬───────────┐
│ chakra         │ 4         │
├────────────────┼───────────┤
│ javascriptcore │ 4         │
├────────────────┼───────────┤
│ spidermonkey   │ 4         │
├────────────────┼───────────┤
│ v8             │ undefined │
├────────────────┼───────────┤

gsathya

Object.defineProperty(Number.prototype,Symbol.iterator,{
  *value({ start = 0, step = 1 } = {}) {
     var inc = this > 0 ? step : -step;
     for (let i = start; Math.abs(i) <= Math.abs(this); i += inc) {
        yield i;
     }
  },
  enumerable: false,
  writable: true,
  configurable: true

gsathya

// Based on https://web.archive.org/web/20160310120458/http://wiki.ecmascript.org/doku.php?id=strawman:scoped_object_extensions

// in whatever-extras.js
import Whatever from './whatever.js';

export extension Extensions = Whatever.protoype {
  somethingComplex: function() { ... }
}

// in user code

gsathya

function observed({kind, key, placement, descriptor, initializer}, privateFieldMaker) {
  assert(kind == "field");
  assert(placement == "own");
  // Create a new anonymous private name as a key for a class element
  let { get, set } = privateFieldMaker();
  let underlyingDescriptor = { enumerable: false, configurable: false, writable: true };
  let underlying = { kind, key: storage, placement, descriptor: underlyingDescriptor, initializer };
  return {
    kind: "method",
    key,

gsathya

➜  v8 (1f0419da93) ✗ python parse-mem.py                                                                                                                      
                    AST Node                       Count                  Total Size                                                                          
               VariableProxy                       22049                    529.2 kb
                     Literal                        5635                   90.176 kb
             FunctionLiteral                         968                    77.52 kb
     ObjectLiteral::Property                        2430                   58.344 kb
                  Assignment                        1066                   25.608 kb
               ObjectLiteral                         648                   20.768 kb
                        Call                         820                   19.704 kb
         ExpressionStatement                        1191                   19.072 kb

gsathya

class X extends Promise {
  static get [Symbol.species]() {
    return Y;
  }
}

class Y {
  constructor(executor) {
    return new Proxy(new Promise(executor), {});
  }

gsathya

{
  class A {
    constructor(arg) {
      return arg;
    }
  }

  class C extends A {
    #x;

gsathya

!(function(e) {
  function t(r) {
    if (n[r]) return n[r].exports;
    var o = (n[r] = { exports: {}, id: r, loaded: !1 });
    return e[r].call(o.exports, o, o.exports, t), (o.loaded = !0), o.exports;
  }
  var n = {};
  return (t.m = e), (t.c = n), (t.p = "./"), t(0);
})(
  (function(e) {

gsathya

// Original:
import("module/id").then(...);

// Node.js (synchronous require; easy):
Promise.resolve().then(_ => require("module/id")).then(...);

// AMD (async require; non-standard):
new Promise(resolve => require("module/id", resolve)).then(...);

// Webpack 2 (require.ensure is Webpack-specific):

gsathya

gunasekaran@gunasekaran-macbookair ~/code/scratch                                                                                                                       [8:11:32]
> $ node
> var bluebird = require('bluebird');
undefined
> function f() {
... Promise.resolve().then(() => console.log('1'));
... bluebird.resolve().then(() => console.log('2'));
... Promise.resolve().then(() => console.log('3'));
... }
undefined