client.js

function ServerSentEvent(path) {
	if (path[0] !== '/') {
		path = '/' + path;
	}

	this.source = new EventSource(path);
	this.events = {};
}

ServerSentEvent.prototype.on = function (name, callback) {
	if (typeof name === 'callback') {
		callback = name;
		name     = 'message';
	}

	var callbackWrapper = function(e) {
		callback(e.data, e);
	};

	var callbackObj = {
		callback : callback,
		wrapper : callbackWrapper
	};

	if (!this.events[name]) {
		this.events[name] = [callbackObj];
	} else {
		this.events[name].push(callbackObj);
	}

	this.source.addEventListener(name, callbackWrapper, false);
};

ServerSentEvent.prototype.once = function (name, callback) {
	var self = this;

	if (typeof name === 'callback') {
		callback = name;
		name     = 'message';
	}

	var callbackWrapper = function(e) {
		callback(e.data, e);
		self.removeListener(name, callbackWrapper);
	};

	this.source.addEventListener(name, callbackWrapper, false);
};

ServerSentEvent.prototype.removeListener = function (name, callback) {
	if (typeof name === 'callback') {
		callback = name;
		name     = 'message';
	}

	var pos,
		events = this.events[name];

	if (events) {
		for (var i = 0, l = events.length; i < l; i++) {
			if (events[i].callback === callback) {
				pos = i;
				break;
			}
		}
	}

	if (pos) {
		callback = events[pos].wrapper;
		events.splice(pos, 1);
	}

	this.source.removeEventListener(name, callback, false);
};

ServerSentEvent.prototype.removeAllListeners = function (name) {
	if (name) {
		this.removeListenersByName(name);
		this.events[name] = null;
	} else {
		for (var key in this.events) {
			this.removeListenersByName(key);
		}

		this.events = {};
	}
};

ServerSentEvent.prototype.removeListenersByName = function (name) {
	var events = this.events[name];

	if (!events) {
		return;
	}

	for (var i = 0, l = events.length; i < l; i++) {
		this.source.removeEventListener(name, events[i].wrapper, false);
	}
};