supermitter.js

var vm = require('vm')
var EventEmitter = require('events').EventEmitter

// ====

/**
 * Supermitter - A compile-on-the-fly event emitter
 *
 * @constructor
 */
function Supermitter () {
  this._events  = {}
  this._counter = 0
}

var proto = Supermitter.prototype

/**
 * on - Listen to an event
 *
 * @param String event
 * @param Function fn
 * @return Supermitter
 */
proto.on = function on (event, fn) {
  this._events[event] || (this._events[event] = [])
  this._events[event].push(this._assign(fn))

  this.recompile()

  return this
}

/**
 * recompile - Re-compiles the emit function
 *
 * @param String event
 * @return Supermitter
 */
proto.recompile = function recompile () {
  var events = null // Array
  var out    = null // Array
  var method = null // String
  var key    = null // String

  // Generate emit()
  out    =
    [ '(function (event, data) {'
    , '  switch (event) {'
    ]
  events = Object.keys(this._events)

  for (var i = 0, il = events.length; i < il; i++) {
    key = events[i]

    out.push('  case "' + key + '":')

    for (var j = 0, jl = this._events[key].length; j < jl; j++) {
      method = this._events[key][j]
      out.push('    this.' + method + '(data)')
    }

    out.push('    return true')
  }

  out.push('  }', '  return false', '})')
  out = out.join("\n")

  this.emit = vm.runInThisContext(out)

  events = out = method = key = null

  return this
}

/**
 * _assign - Assign a unique name to a function
 *
 * @param Function fn
 * @return String
 */
proto._assign = function assign (fn) {
  var method = '__fn' + this._counter

  this[method] = fn
  ;++this._counter

  return method
}

/**
 * emit - To be replaced with generated function
 *
 * @param String event
 * @param Mixed data
 * @return Boolean
 */
proto.emit = function emit (event, data) {
  return false
}

// ====

var e     = new Supermitter
var start = null

e.on('test:event', function (data) {})
e.on('test:event', function (data) {})
e.on('test:event', function (data) {})
e.on('test:event', function (data) {})
e.on('testing', function () {})

start = Date.now()
for (var i = 0; i < 10000000; i++) {
  e.emit('test:event', [1, 2, 3])
}
console.log('Superemitter:multiple', Date.now() - start)

start = Date.now()
for (var i = 0; i < 10000000; i++) {
  e.emit('testing', [1, 2, 3])
}
console.log('Supermitter:single', Date.now() - start)

// --

var ee = new EventEmitter

ee.on('test:event', function (data) {})
ee.on('test:event', function (data) {})
ee.on('test:event', function (data) {})
ee.on('test:event', function (data) {})
ee.on('testing', function () {})

start = Date.now()
for (var i = 0; i < 10000000; i++) {
  ee.emit('test:event', [1, 2, 3])
}
console.log('EventEmitter:multiple', Date.now() - start)

start = Date.now()
for (var i = 0; i < 10000000; i++) {
  ee.emit('testing', [1, 2, 3])
}
console.log('EventEmitter:single', Date.now() - start)