 class Subject{
   constructor(){
       this.state = 0
       this.observers = []
   }
   getState(){
       return this.state
   }
   setState(state){
       this.state = state
       this.notifyAllObservers()
   }
   notifyAllObservers(){
       this.observers.forEach(item=>{
        item.update()
       })
   }
   attach(observer){
       this.observers.push(observer)
   }
}
class Observer{
   constructor(name,subject){
       this.name = name
       this.subject = subject
       this.subject.attach(this)
   }
   update(){
       console.log(`${this.name}被触发了值为${this.subject.getState()}`);
   }
}
const s = new Subject()
const o1= new Observer('o1',s)
s.setState(1)