const sleep = ms => new Promise(resolve => setTimeout(resolve, ms))

const createAsyncQueue = delay => {
  /** @type {{ func: () => PromiseLike, id: number }[]} */
  const queue = []
  let id = 0
  const results = {}; // semi colon needed

  setInterval(async () => {
    if (queue.length > 0) {
      const [ { func, id } ] = queue.splice(0, 1)
      results[id] = await func()
    }
  }, delay)

  return {
    /**
     * Evaluate a delayed function
     * @param {() => PromiseLike} func
     */
    async eval(func) {
      let curId = id++
      queue.push({ func, id: curId })
      await sleep(delay * queue.length) // Wait for the queue to deflate
      const result = results[curId]
      if (!result)
        throw new Error('No result')
      return result
    }
  }
}