SOURCE

// https://juejin.cn/post/6844904134840156168
class Observer {
    update() {
        console.log('被观察者发出通知后执行');
    }
}
class Subject {
    constructor() {
        this.observerQueue = [];
    }
    addObserver(obj) {
        this.observerQueue.push(obj)
    }
    notify() {
        this.observerQueue.forEach(item => item.update())
    }
}





var ob1 = new Observer()    //观察者1
var ob2 = new Observer()    //观察者2

var subject = new Subject()       //被观察者
subject.addObserver(ob1)          //观察者1订阅subject的通知
subject.addObserver(ob2)          //观察者2订阅subject的通知
subject.notify()