EventEmitter.listenerCount(emitter, event)

if(events.EventEmitter.listenerCount(this, 'feedback') == 0) {
    //....
}

EventEmitter.listenerCount = function(emitter, type) {
  var ret;
  if (!emitter._events || !emitter._events[type])
    ret = 0;
  else if (util.isFunction(emitter._events[type]))
    ret = 1;
  else
    ret = emitter._events[type].length;
  return ret;
};