process-queue.js

const queue = new Signal()
const done = new Signal()

const pending = []
async function runQueue () {
  while (!pending.length && await queue.wait());

  const current = pending
  pending = []
  await process(current)
  done.notify()
}

async function addToQueue (job) {
  pending.push(job)
  queue.notify()
  return done.wait()
}