Event Emitter

EventEmitter.js

class EventEmitter {
  constructor() {
    this.events = {};
  }

  on(event, func) {
    if(this.events[event]) {
      this.events[event].push(func);
    } else {
      this.events[event] = [func];
    }
  }

  trigger(event, ...rest) {
    if(this.events[event]) {
      this.events[event].forEach(func => {
        func.apply(rest);
      });
    }
  }
}

const ee = new EventEmitter();
ee.on('click', () => {
  console.log('Click event was triggered');
});

ee.trigger('click');   // returns 'Click event was triggered'