js 观察者模式

2023-03-17

观察者模式定义对象间一种一对多的依赖关系，使得每当一个对象改变状态，则所有依赖于它的对象都会得到通知并被自动更新。

let observerIds = 0
let observedIds = 0

// 观察者
class Observer {
    constructor() {
        this.id = observerIds++
    }

    update(observed) {
        console.log(`观察者${this.id}观察到${observed.id}的变化`)
    }
}

// 被观察者
class Observed {
    constructor() {
        this.observerList = []
        this.id = observedIds++
    }

    addObserver(observer) {
        this.observerList.push(observer)
    }

    removeObserver(observer) {
        this.observerList = this.observerList.filter(i => i.id !== observer.id)
    }

    notify() {
        this.observerList.forEach(i => {
            i.update(this)
        })
    }

}

const mObserved = new Observed();
const mObserver1 = new Observer();
const mObserver2 = new Observer();

mObserved.addObserver(mObserver1);
mObserved.addObserver(mObserver2);

mObserved.notify();