simple_event.js

const events = {
  events: {},
  on: function (eventName, fn) {
    this.events[eventName] = this.events[eventName] || [];
    this.events[eventName].push(fn);
  },
  emit: function (eventName, data) {
    if (this.events[eventName]) {
      this.events[eventName].map(function(fn) {
        fn(data);
      });
    }
  }
}