code: function hasListeners (emitter, type) {
    var count = typeof emitter.listenerCount !== 'function'
      ? emitter.listeners(type).length
      : emitter.listenerCount(type)
  
    return count > 0
  }
docs: Determine if emitter has listeners of a given type.
  
  The way to do this check is done three different ways in Node.js >= 0.8
  so this consolidates them into a minimal set using instance methods.
  
  @param {EventEmitter} emitter
  @param {string} type
  @returns {boolean}
  @private