Hello, world!

ahoy.js

function delayExecution(resolver) {
  return new Promise((resolve) => setTimeout(() => resolve(resolver), 1000));
}

function* messageGenerator() {
  yield 'H';
  yield 'e';
  yield 'l';
  yield 'l';
  yield 'o';
  yield ',';
  yield ' ';
  yield 'w';
  yield 'o';
  yield 'r';
  yield 'l';
  yield 'd';
  yield '!';
}

async function* asyncMessageIterator(generator) {
  for (let letter of generator()) {
    await delayExecution(letter);
    yield letter;
  }
}

function MessageConstructor() {
  this.parts = [];
  this[Symbol.asyncIterator] = async function* () {
    const iterator = asyncMessageIterator(messageGenerator);
    for await (let part of iterator) {
      this.parts.push(part);
      yield part;
    }
  };
}

async function assembleMessage() {
  const messageBuilder = new MessageConstructor();
  let message = '';

  for await (let part of messageBuilder) {
    message += part;
  }

  return message;
}

assembleMessage().then(console.log);