test if the function passed to ee.on() and ee.removeListener() can validly be "inner functions"

test-same-inner-function-listeners.js

'use strict'

// Not sure how valid this test is, but the attempt is to try to see if
// the function passed to ee.on() and ee.removeListener() can validly be
// "inner functions".  Specifically, does the ee class consider `onEmitted()`
// functions to be different based on their closure.  You would hope yes, and
// I think that's what the test shows.
//
// If they weren't considered different, instead of the listener list shrinking
// from both ends, it would shrink from just one end.

const EventEmitter = require('events')

class Emitter extends EventEmitter {
  constructor () {
    super()

    let counter = 0

    setInterval(() => {
      counter++
      console.log('')
      this.emit('emitted', counter)
    }, 1000).unref()
  }
}

const ListenerCount = 5
const emitter = new Emitter()

for (let i = 1; i <= ListenerCount; i++) {
  createListener(i)
}

for (let i = ListenerCount; i >= 1; i--) {
  createListener(i)
}

function createListener (i) {
  emitter.on('emitted', onEmitted)

  setTimeout(stop, i * 1010)

  function onEmitted (counter) {
    console.log(`listener ${i}: ${counter}`)
  }

  function stop () {
    emitter.removeListener('emitted', onEmitted)
  }
}