Compare Node.js event signaling using callbacks vs. the event emitter class

evc.coffee

EventEmitter = require('events').EventEmitter

class TestSubject extends EventEmitter
  constructor: (callback) ->
    @callback = callback

  start: ->
    started = Date.now()
    while (Date.now() - started) < 10000
      @emit 'fire'
      if @callback
        @callback()
    @emit 'end'

limit = 10
result = []
accumulator = []

testCallback = ->
  count = 0
  b = new TestSubject ->
    count += 1
  b.on 'end', ->
    console.log "Callback counted to #{count}"
    accumulator.push count
    testEmitter()
  console.log 'starting TestCallback'
  b.start()

testEmitter = ->
  count = 0
  b = new TestSubject()
  b.on 'fire', ->
    count += 1
  .on 'end', ->
    console.log "Emitter counted to #{count}"
    accumulator.push count

    result.push accumulator
    accumulator = []

    limit -= 1
    if limit > 0
      # Next pass
      testCallback()
    else
      # Dump results
      console.log result
  console.log 'starting TestEmitter'
  b.start()

# Start the first test
testCallback()

I've recorded similar results using Node.js v0.6.20, with an overall improvement by using event emitters over callbacks of 73%.

On the same machine that I used to run the v0.6.20 and v0.8.11 testing, I've installed v0.4.10 to match the latest available on Heroku. On this version callbacks averaged 24468784 iterations, and emitters averaged 35189490 iterations, for an improvement of 44%. This is not as impressive as in newer versions of Node.js but it is still significant.