Push iterator

iter.js

const Queue = require('then-queue'); // async queue that doesn't care what order you call push and pop.

const queue = new Queue();

// push sends to the first waiting `pop` if available, otherwise it acts as a buffer
listenToNewMessages(message => queue.push(message));

async function* MessagesGenerator() {
  try {
    while (true) {
      // pop takes the first item if available, otherwise it waits for an item to be available
      yield await queue.pop();
    }
  }
}

const messages = MessagesGenerator()

for await (let message of messages)) {
  // even if you do something async here, no messages are ignored.  e.g.
  await new Promise(resolve => setTimeout(resolve, 1000));
  console.log(message)
}