前端设计模式——观察者模式

class Subject {
  constructor() {
    this.observers = []
  }
  
  addObserver(observer) {
    this.observers.push(observer)
  }
  
  removeObserver(observer) {
    this.observers = this.observers.filter(obs => obs !== observer)
  }
  
  notify(data) {
    this.observers.forEach(obs => obs.update(data))
  }
}

class Observer {
  update(data) {
    console.log(`Received data: ${data}`)
  }
}

// Usage
const subject = new Subject()
const observer1 = new Observer()
const observer2 = new Observer()

subject.addObserver(observer1)
subject.addObserver(observer2)

subject.notify('Hello, world!')
// Output:
// Received data: Hello, world!
// Received data: Hello, world!

subject.removeObserver(observer1)

subject.notify('Goodbye, world!')
// Output:
// Received data: Goodbye, world!