PubSub

var PubSub = (function() {
	let listeners = {};
	return {
		listeners,
		subscribe (evt, fn) {
			if(!this.listeners.hasOwnProperty(evt)) {
				this.listeners[evt] = [];
			}
			this.listeners[evt].push(fn);
			return () => {
				if(this.listeners.hasOwnProperty(evt)) {
					this.listeners[evt].splice(this.listeners[evt].indexOf(fn), 1);
					if(!this.listeners[evt].length) {
						delete this.listeners[evt];
					}
				}
			};
		},
		publish(evt, data) {
			if(this.listeners.hasOwnProperty(evt)) {
				this.listeners[evt].forEach(listener => listener(data))
			}
		}
	}
}());