emitter.js

/**
 * @module primish/emitter
 * @description emitter for primish, standalone mediator or mixin
 **/
;(function(factory){
	// UMD wrap
	if (typeof define === 'function' && define.amd){
		define('primish/emitter', ['./primish'], factory);
	} else if (typeof module !== 'undefined' && module.exports){
		module.exports = factory(require('./primish'));
	} else {
		this.emitter = factory(this.primish);
	}
}).call(this, function(primish){
	var slice = Array.prototype.slice;

	var EID = 0;

	var pseudoEvents = {
		once: function(eventName, fn){
			var self = this,
				wrapped = function(){
					fn.apply(this, arguments);
					self.off(eventName, wrapped);
				};
			return wrapped;
		}
	};

	var emitter = primish({

		on: function(event, fn){
			// supports multiple events split by white space
			event = event.split(/\s+/);
			var i = 0,
				len = event.length,
				listeners = this._listeners || primish.hide(this, '_listeners'),
				events,
				k,
				pseudos,
				eventName,
				knownPseudo;

			loopEvents:
				for (; i < len; ++i){
					pseudos = event[i].split(':');
					eventName = pseudos.shift();
					knownPseudo = pseudos.length && pseudos[0] in pseudoEvents;

					knownPseudo || (eventName = event[i]);
					events = listeners[eventName] || (listeners[eventName] = {});

					for (k in events) if (events[k] === fn) continue loopEvents;
					events[(EID++).toString(36)] = knownPseudo ? pseudoEvents[pseudos[0]].call(this, eventName, fn) : fn;
				}
			return this;
		},

		off: function(event, fn){
			var listeners = this._listeners, events, key, length = 0, l, k;
			if (listeners && (events = listeners[event])){

				for (k in events){
					length++;
					/* don't touch this, === breaks tests due to undefined after delete */
					if (key == null && events[k] === fn) key = k;
					if (key && length > 1) break;
				}

				if (key){
					delete events[key];
					if (length === 1){
						// delete so that the order of the array remains unaffected, making it sparse
						delete listeners[event];
						for (l in listeners) return this;
						delete this._listeners;
					}
				}
			}
			return this;
		},

		trigger: function(event){
			var listeners = this._listeners,
				events,
				k,
				args = slice.call(arguments, 1),
				copy = {};

			if (listeners && (events = listeners[event])){
				for (k in events) copy[k] = events[k];
				for (k in copy) copy[k].apply(this, args);
			}

			return this;
		}

	});

	emitter.definePseudo = function(pseudo, fn){
		pseudoEvents[pseudo] = fn;
	};

	return emitter;
});