Simple Event Emitter

event-emitter.js

// Simple Event emitter realization

class EventEmitter {
  constructor() {
    // store for handlers
    this.events = {};
  }
  // subscribe 
  on(name, fn) {
    this.events[name] = this.events[name] || [];
    this.events[name].push(fn);
  };
  
  // fire an event
  trigger(name, args) {
    this.events[name] = this.events[name] || [];
    this.args = args || [];
    this.events[name].forEach(function(fn) {
      fn.apply(this, args);
    });
  };
}

simple-usage.js

// create instance
var emitter = new EventEmitter();

// listening to all 'ringBell' events
emitter.on('ringBell', function(data) {
  console.log('Who\'s there?');
  console.log('I see you', data.visitor);
});

// firing events 'ringBell'
emitter.trigger('ringBell', [{ visitor: 'Neighbour' }]);
emitter.trigger('ringBell', [{ visitor: 'Angry man' }]);