在firebase中引用子数据

{
  "users": {
    "user1": {
      "name": "Alice",
      "age": 25,
      "address": {
        "city": "New York",
        "zip": "10001"
      }
    },
    "user2": {
      "name": "Bob",
      "age": 30,
      "address": {
        "city": "Los Angeles",
        "zip": "90001"
      }
    }
  }
}

const firebase = require('firebase/app');
require('firebase/database');

// 初始化Firebase
firebase.initializeApp({
  databaseURL: 'https://your-database-url.firebaseio.com'
});

const database = firebase.database();

// 引用用户1的数据
const user1Ref = database.ref('users/user1');

// 监听数据变化
user1Ref.on('value', (snapshot) => {
  const userData = snapshot.val();
  console.log(userData.address.city); // 输出: New York
});

user1Ref.once('value', (snapshot) => {
  const userData = snapshot.val();
  console.log(userData.address.city); // 输出: New York
});

{
  "users": {
    "user1": {
      "name": "Alice",
      "age": 25,
      "address": {
        "city": "New York",
        "zip": "10001"
      }
    },
    "user2": {
      "name": "Bob",
      "age": 30,
      Realtime Database
      "address": {
        "city": "Los Angeles",
        "zip": "90001"
      }
    }
  }
}

const firebase = require('firebase/app');
require('firebase/firestore');

// 初始化Firebase
firebase.initializeApp({
  projectId: 'your-project-id'
});

const firestore = firebase.firestore();

// 引用用户1的数据
const user1Ref = firestore.doc('users/user1');

// 获取数据
user1Ref.get().then((doc) => {
  if (doc.exists) {
    const userData = doc.data();
    console.log(userData.address.city); // 输出: New York
  } else {
    console.log('No such document!');
  }
});

const usersCollectionRef = firestore.collection('users');

usersCollectionRef.doc('user1').get().then((doc) => {
  if (doc.exists) {
    const userData = doc.data();
    console.log(userData.address.city); // 输出: New York
  } else {
    console.log('No such document!');
  }
});