JavaScript高效发布订阅模式实现方法

class PubSub {
  constructor() {
    this.events = Object.create(null); // 避免原型污染
  }

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

  // 发布事件
  emit(event, data) {
    if (!this.events[event]) return;
    this.events[event].forEach(callback => {
      try {
        callback(data);
      } catch (err) {
        console.error(`Error in event "${event}" handler:`, err);
      }
    });
  }

  // 取消订阅
  off(event, callback) {
    if (!this.events[event]) return;

    if (!callback) {
      delete this.events[event];
      return;
    }

    this.events[event] = this.events[event].filter(cb => cb !== callback);
  }
}

const bus = new PubSub();

// 订阅消息
bus.on('userLogin', user => {
  console.log('欢迎用户：', user.name);
});

bus.on('userLogin', () => {
  console.log('更新登录状态');
});

// 发布消息
bus.emit('userLogin', { name: 'Alice' });

// 取消某个订阅
const welcomeHandler = user => console.log('打招呼：', user.name);
bus.on('userLogin', welcomeHandler);
bus.off('userLogin', welcomeHandler); // 移除该监听

  once(event, callback) {
    const wrapped = (...args) => {
      callback.apply(this, args);
      this.off(event, wrapped);
    };
    this.on(event, wrapped);
  }