如何在firebase中获取特定列的数据？

// 初始化Firebase
var firebaseConfig = {
  apiKey: "YOUR_API_KEY",
  authDomain: "YOUR_AUTH_DOMAIN",
  databaseURL: "YOUR_DATABASE_URL",
  projectId: "YOUR_PROJECT_ID",
  storageBucket: "YOUR_STORAGE_BUCKET",
  messagingSenderId: "YOUR_MESSAGING_SENDER_ID",
  appId: "YOUR_APP_ID"
};

firebase.initializeApp(firebaseConfig);

// 获取对数据库的引用
var database = firebase.database();

- users
  - user1
    - name: "John"
    - age: 25
  - user2
    - name: "Jane"
    - age: 30

var nameRef = database.ref("users/user1/name");
nameRef.on("value", function(snapshot) {
  var name = snapshot.val();
  console.log(name); // 输出 "John"
});