class SimplePubSub {
    subscribe(event, listener) {

    }
    unsubscribe(event, listener) {

    }
    publish(event, data) {

    }
}

// 创建 PubSub 实例
const pubSub = new SimplePubSub();

// 定义订阅者
const subscriber1 = (data) => {
    console.log(`Subscriber 1 received: ${data}`);
};

const subscriber2 = (data) => {
    console.log(`Subscriber 2 received: ${data}`);
};

// 订阅事件
pubSub.subscribe('event1', subscriber1);
pubSub.subscribe('event1', subscriber2);

// 发布事件
pubSub.publish('event1', 'Hello, World!');

// 取消订阅
pubSub.unsubscribe('event1', subscriber1);

// 发布事件
pubSub.publish('event1', 'Hello again!');

// 输出应该是如下的样式
/*
Subscriber 1 received: Hello, World!
Subscriber 2 received: Hello, World!
Subscriber 2 received: Hello again!
*/