[ECMAScript] array with async iterator

async-array.js

const Notifier = class {
  constructor() {
    this.waits = new Set();
  }
  get wait() {
    let d = {};
    const p = new Promise((f, r) => {
      d.r = r; d.f = f;
    });
    this.waits.add(d);
    return p;
  }
  notify() {
    for (const {f} of this.waits) f();
    this.waits.clear();
  }
  close() {
    for (const {r} of this.waits) r();
    this.waits.clear();
  }
};
const notifiers = new WeakMap();

export const AsyncArray = class extends Array {
  constructor(...args) {
    super(...args);
    notifiers.set(this, new Notifier());
  }
  push(...args) {
    const r = super.push(...args);
    notifiers.get(this).notify();
    return r;
  }
  close() {
    notifiers.get(this).close();
  }
  async *[Symbol.asyncIterator]() {
    let i = 0;
    try {
      for (let i = 0; ; i++) {
        while (i >= this.length) {
          await notifiers.get(this).wait;
        }
        yield this[i];
      }
    } catch {}
  }
};

async-array_test.js

import {assertEquals} from "https://deno.land/std/testing/asserts.ts";
import {AsyncArray} from "./async-array.js";

Deno.test("async array", async () => {
  const a = new AsyncArray();

  a.push(0);
  a.push(1);
  a.push(2);
  (async () => {
    for (let i = 3; i < 6; i++) {
      await new Promise(f => setTimeout(f, 100));
      a.push(i);
    }
    a.close();
  })();
  
  const r = [];
  for await (const e of a) {
    r.push(e);
  }
  assertEquals(r, [0,1,2,3,4,5]);
});