Generatorify EventEmitter

generatorify.js

// Referred to https://raw.githubusercontent.com/denoland/deno_std/v0.3.2/http/server.ts

function deferred() {
  let resolve, reject
  const promise = new Promise((res, rej) => {
    resolve = res
    reject = rej
  })
  return {
    promise,
    resolve,
    reject
  }
}

async function* listen(emitter, event) {
  const env = {
    queue: [],
    deferred: deferred()
  }

  emitter.on(event, (...args) => {
    env.queue.push(args)
    env.deferred.resolve()
  })

  while (true) {
    await env.deferred.promise
    env.deferred = deferred()
    const queueToProcess = env.queue
    env.queue = []
    for (const result of queueToProcess) {
      yield result
      env.deferred.resolve()
    }
  }
}

function generatorify(emitter) {
  return event => listen(emitter, event)
}

module.exports = generatorify

usage.js

const emitter = new (require('events'))
const generatorify = require('./generatorify')

// emitter.on('eventName', (arg1, arg2) => {
//   console.log(arg1, arg2)
// })

!(async () => {
  const listen = generatorify(emitter)
  for await (const [arg1, arg2] of listen('eventName')) {
    console.log(arg1, arg2)
  }
})()

emitter.emit('eventName', 1, 2)