// 声明类
export class EventBus {
  private eventList: object;
  constructor() {
    //定义事件总线对象
    this.eventList = {};
  }
  //监听，或者说是发布
  on(eventName, fn) {
    let eventItem = this.eventList[eventName];
    eventItem ? eventItem.push(fn) : (this.eventList[eventName] = [fn]);
  }
  //触发，订阅
  emit(eventName, ...arg) {
    this.eventList[eventName] &&
      this.eventList[eventName].forEach((fn) => {
        fn(...arg);
      });
  }
}

export default EventBus;