Emitter Class Implementation

Emitter.js

function Emitter(){
	var events = new Map();
	
	return {
		subscribe: function(event_name, callback){
			//If events has event_name, then get the event Subscription and push to it.
			//Else create new event, subscription and add to events.
			
			var isEventExisted = events.has(event_name), index = 0;
			
			if (isEventExisted){
				var subscriptions = events.get(event_name);				
				index = subscriptions.push(callback) - 1;
			}
			else{
				events.add(event_name, [callback]);
			}		
			
			//Return an object with reference to this
			return {
				release: function(){
					var status = true;
					
					if (index > -1){
						var subscriptions = events.get(event_name);
						if (subscriptions){
							subscriptions.splice(index, 1);
						}
						
						return status;
					}
					
					return !status;
				}
			};
		},
		emit: function(event_name, ...params){
			var isExisted = events.has(event_name);
			
			if (isExisted){
				var subscriptions = events.get(event_name);
				
				if (subscriptions){
					for(var i = 0; i < subscriptions.length; i++){
						var subscription = subscriptions[i];
						
						if (subscription instanceof Function){			
							
							//Trigger outside of loop
							(function(func, args){
								setTimeout(function(){
									//... to turn it back to arguments, instead of array
									func(...args);
								});
							})(subscription, params);
						}
					}
				}
			}
			
			return isExisted;
		}
	}
}

EmitterTest.js

var emitter = new Emitter();
var subscriber1 = emitter.subscribe('event_1', function(name){console.log(name);});
var subscriber2 = emitter.subscribe('event_1', function(name, id){console.log(`${name} ${id}`);});
var subscriber3 = emitter.subscribe('event_1', function(name, id, gender){console.log(`${name} ${id} - gender: ${3}`);});

emitter.emit('event_1', "Maya", "32", "female");
var subscriber12 = emitter.subscribe('event_12', function(name){console.log(name + 'he');});
subscriber2.release();

emitter.emit('event_1', "Natan", "30", "male");