观察者模式

// 被观察者
class Subject{
    constructor(name){
        this.name = name
        this.state = "开心的"
        this.observer = []
    }

    updateState(state){
        this.state = state
        // 通知观察者更新
        this.observer.forEach(item=>item.update(this))
    }

    attach(o){
        this.observer.push(o)
    }
}

// 观察者
class Oberserver{
    constructor(name){
        this.name = name
    }

    update(person){
        console.log(`${this.name}发现${person.name}状态变为${person.state}`)
    }
}

let baby = new Subject('baby')
let father = new Oberserver("father")
let mather = new Oberserver("mather")
baby.attach(father)
baby.attach(mather)

setTimeout(function(){
    baby.updateState("哭了")
},3000)

setTimeout(function(){
    baby.updateState("再跑。。。")
},5000)