function Observer () {
  this.message = {};
}

Observer.prototype = {
  constructor: Observer,

  subscribe(type, fn) {
    (this.message[type]) || (this.message[type] = []).push(fn);
  },
  fire(type, ...args) {
    if (!this.message[type]) {
      return;
    }
    for (let i = 0, len = this.message[type].length; i < len; i++) {
      this.message[type][i].apply(this, args);
    }
  },
  remove(type, fn) {
    if (this.message[type]) {
      for (let i = 0, len = this.message[type].length; i < len; i++) {
        if (this.message[type][i] === fn) {
          this.message[type].splice(i, 1);
        }
      }
    }
  }
}

var o = new Observer();
o.subscribe('test-event', function(...args) {
  console.log('data', args);
})

o.fire('test-event', { data: 123});