async-mailbox.js - async generator publisher

async-mailbox.js

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

export const hz = x => (1/x * 1000)

const complete = Symbol('complete')

export class Mailbox {
  #buffer = []

  constructor(rate=16, max=500) {
    this.rate = rate
    this.max = max
  }

  send(value) {
    if (this.#buffer.length < this.max) {
      this.#buffer.push(value)
      return true
    }
    return false
  }

  async next() {
    while (true) {
      if (this.#buffer.length > 0) {
        let value = this.#buffer.shift()
        return {value, done: false}
      }
      await sleep(this.rate)
    }
  }

  [Symbol.asyncIterator]() {
    return this
  }
}

export const EventMailbox = (element, event) => {
  let mailbox = new Mailbox()
  element.addEventListener(event, event => {
    mailbox.send(event)
  })
  return mailbox
}