node.js EventEmitter.once (with example) (answer for http://stackoverflow.com/questions/12150540/javascript-eventemitter-multiple-events-once)

EventEmitter.once.js

// "Extend" the EventEmitter like this:

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

EventEmitter.prototype.once = function(events, handler){
	// no events, get out!
	if(! events)
		return; 

	// Ugly, but helps getting the rest of the function 
	// short and simple to the eye ... I guess...
	if(!(events instanceof Array))
		events = [events];

	var _this = this;

	var cb = function(){
		events.forEach(function(e){ 	
			// This only removes the listener itself 
			// from all the events that are listening to it
                        // i.e., does not remove other listeners to the same event!
			_this.removeListener(e, cb); 
		});

		// This will allow any args you put in xxx.emit('event', ...) to be sent 
		// to your handler
		handler.apply(_this, Array.prototype.slice.call(arguments, 0));
	};

	events.forEach(function(e){ 
		_this.addListener(e, cb);
	});	
};


// EXAMPLE
var game = new EventEmitter();
game.endGame = function(){
	console.log('Game ended!');
};
game.on('player:quit', function(){
	console.log('quit')
});
game.on('player:disconnect', function(){
	console.log('disconnect')
});
game.once(['player:quit', 'player:disconnect'], function (a, b, c) {
	console.log('Disconnecting...');
	console.log('arg 1: ' + a);
	console.log('arg 2: ' + b);
	console.log('arg 3: ' + c);	
	game.endGame()
});

// This will exec our handler...
game.emit('player:disconnect', 1, 2, 3);

// This one will exec no handler...
game.emit('player:quit', 4, 5, 6);

/*
This outputs:
Disconnecting...
arg 1: 1
arg 2: 2
arg 3: 3
Game ended!
*/