如何在javascript应用程序中获取不同的FCM注册令牌？

<script src="https://www.gstatic.com/firebasejs/9.0.2/firebase-app.js"></script>
<script src="https://www.gstatic.com/firebasejs/9.0.2/firebase-messaging.js"></script>

// 初始化Firebase
firebase.initializeApp({
  apiKey: "YOUR_API_KEY",
  authDomain: "YOUR_AUTH_DOMAIN",
  projectId: "YOUR_PROJECT_ID",
  messagingSenderId: "YOUR_SENDER_ID",
  appId: "YOUR_APP_ID"
});

const messaging = firebase.messaging();

messaging.requestPermission()
  .then(() => {
    console.log('授权成功');
    return messaging.getToken();
  })
  .then((token) => {
    console.log('注册令牌：', token);
    // 在这里可以将注册令牌发送到服务器保存
  })
  .catch((error) => {
    console.log('授权失败：', error);
  });