code: function emitNone(handler, isFn, self) {
    if (isFn)
      handler.call(self);
    else {
      var len = handler.length;
      var listeners = arrayClone(handler, len);
      for (var i = 0; i < len; ++i)
        listeners[i].call(self);
    }
  }
docs: These standalone emit* functions are used to optimize calling of event handlers for fast cases because emit() itself often has a variable number of arguments and can be deoptimized because of that. These functions always have the same number of arguments and thus do not get deoptimized, so the code inside them can execute faster.