is-node-emitter/index.js

Strictly checks that given value is nodejs EventEmitter. It's easy, because his API is in frozen state.

/*!
 * is-node-emitter <https://github.com/tunnckoCore/is-node-emitter>
 *
 * Copyright (c) 2015 Charlike Mike Reagent <@tunnckoCore> (http://www.tunnckocore.tk)
 * Released under the MIT license.
 */

'use strict'

var isArray = require('isarray')
var isRealObject = require('is-real-object')

module.exports = function isNodeEmitter (val) {
  return isRealObject(val) &&
    typeof val.on === 'function' &&
    typeof val.once === 'function' &&
    typeof val.emit === 'function' &&
    typeof val.addListener === 'function' &&
    typeof val.removeListener === 'function' &&
    typeof val.setMaxListeners === 'function' &&
    typeof val.removeAllListeners === 'function' &&
    typeof val.listeners === 'function' &&
    tryIt(val)
}

function tryIt (ee) {
  var name = '~~~~~~~foo~~~~~~~bar~~~~~~~'
  function handler () {
    ee.removeListener(name, handler)
  }
  ee.once(name, handler)
  var listeners = ee.listeners(name, true)

  if (isArray(listeners) && listeners.length >= 1) {
    ee.emit(name)
    return true
  }
  return false
}