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How we research

You have an idea for a new JavaScript proposal, but don't know exactly what shape it should take? This document is for you!

Getting started

If you are new to research, it might be overwhelming at first. For this, there is a great intro video series to help get your feet on the ground.

Techniques:

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Data Structures

This file is for bike shedding data structures for TC39

Proposals repo data structure

Current data structure

[

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function lex(string) {
  return string
    .match(/a|b|c|d/g)
    .map(token => token.toUpperCase());
}

// This language has no structure, so we are jumping straight to bytecode rather than first building
// an AST
function parse(tokens) {
  const bytecode = [];

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"use strict";

Iterator.prototype = {
  *map(mapper) {
    for (let value of this) {
      yield mapper(value);
    }
  },
};

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Core Proposal real-world examples

Living Document. J. S. Choi, 2018-12.

WHATWG Fetch Standard

The [WHATWG Fetch Standard][] contains several examples of using the DOM fetch function, resolving its promises into values, then processing the values in various ways. These examples may become more easily readable with smart pipelines.

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Stage 2

Needs pre-review?	Proposal	Author	Champion	Last Presented
no	[function.sent metaproperty][function-sent]	Allen Wirfs-Brock	贺师俊 (HE Shi-Jun)	[July 2019][function-sent-notes]
yes	[Decorators][decorators]

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var regex = /t(e)(st(\d?))/g;
var string = 'test1test2';

string.match(regex); // gives ['test1', 'test2'] - how do i get the capturing groups?

var matches = [];
var lastIndexes = {};
var match;
lastIndexes[regex.lastIndex] = true;
while (match = regex.exec(string)) {

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TC39 meeting, December 3-5th 2019

Summary

Need Review:

• Dynamic Import Host Adjustment for Stage 2

Needs implementation:

• Atomics.waitAsync for Stage 3

Needs minor change:

• Make super() throw after evaluating args
• make async iterators next/return/throw not pass undefined when value is absent
• Eliminate extra environment for eval in parameter initializers redux

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TC39 meeting, October 1-3rd 2019

Summary

Not much significant change that we need to be worried about but lot of new proposals moved to stage 1. We have some reviewing work to do, as there is so much new stuff.

Need Review:

• Map.upsert , previously Map.insertOrUpdate

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// TabDescriptorActor
const TabDescriptorActor = ActorClassWithSpec(descriptorSpec, {
  initialize(connection, options = {}) {
    Actor.prototype.initialize.call(this, connection);
    this.tabList = options.tabList;
    this.destroy = this.destroy.bind(this);
  },

  async getTarget() {
    const tabList = this.tabList;