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观察者模式
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// 在观察者模式中,观察者是知道Subject的,Subject一直保持对观察者进行记录。 | |
// 观察者模式大多数时候是同步的,比如当事件触发,Subject就会去调用观察者的方法。 | |
// 观察者 | |
class Observer { | |
constructor() { | |
} | |
update(val) { | |
console.log(val); | |
} | |
} | |
// 观察者列表 | |
class ObserverList { | |
constructor() { | |
this.observerList = [] | |
} | |
add(observer) { | |
return this.observerList.push(observer); | |
} | |
remove(observer) { | |
this.observerList = this.observerList.filter(ob => ob !== observer); | |
} | |
count() { | |
return this.observerList.length; | |
} | |
get(index) { | |
return this.observerList[index]; | |
} | |
} | |
// 目标 | |
class Subject { | |
constructor() { | |
this.observers = new ObserverList(); | |
} | |
addObserver(observer) { | |
this.observers.add(observer); | |
} | |
removeObserver(observer) { | |
this.observers.remove(observer); | |
} | |
notify(...args) { | |
let obCount = this.observers.count(); | |
for (let i = 0; i < obCount; i++) { | |
this.observers.get(i).update(...args); | |
} | |
} | |
} | |
// let sub = new Subject(); | |
// sub.addObserver(new Observer()); | |
// sub.notify(123); | |
// sub.addObserver(new Observer()); | |
// sub.notify(1234); |
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