// 创建一个DOM元素作为事件中心（也可用普通对象）
const eventTarget = document.createElement('div');

// 监听自定义事件
eventTarget.addEventListener('userLogin', function(e) {
  console.log('用户已登录:', e.detail.username);
});

// 触发事件
const loginEvent = new CustomEvent('userLogin', {
  detail: { username: 'Alice' }
});
eventTarget.dispatchEvent(loginEvent);

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

  // 监听事件
  on(event, callback) {
    if (!this.events[event]) {
      this.events[event] = [];
    }
    this.events[event].push(callback);
  }

  // 触发事件
  emit(event, data) {
    if (this.events[event]) {
      this.events[event].forEach(callback => callback(data));
    }
  }

  // 移除监听
  off(event, callback) {
    if (this.events[event]) {
      this.events[event] = this.events[event].filter(cb => cb !== callback);
    }
  }
}

const emitter = new EventEmitter();

emitter.on('dataLoaded', function(data) {
  console.log('数据加载完成:', data);
});

emitter.emit('dataLoaded', { items: [1, 2, 3] });

function Carousel(element) {
  this.element = element;
  this.eventEmitter = new EventEmitter();
  this.currentIndex = 0;
}

Carousel.prototype.next = function() {
  this.currentIndex++;
  // 触发自定义事件
  this.eventEmitter.emit('slideChange', {
    index: this.currentIndex
  });
};

// 使用插件时绑定事件
const carousel = new Carousel(document.getElementById('slider'));
carousel.eventEmitter.on('slideChange', function(data) {
  console.log('当前幻灯片:', data.index);
});