import { getFirestore, doc, getDoc } from "firebase/firestore";

// 初始化Firestore
const db = getFirestore();

// 获取文档数据
async function getDocumentData() {
  const docRef = doc(db, "collectionName", "documentId");
  const docSnap = await getDoc(docRef);
  
  if (docSnap.exists()) {
    const data = docSnap.data(); // 将数据加载到变量中
    console.log("Document data:", data);
    return data;
  } else {
    console.log("No such document!");
    return null;
  }
}

import { doc, onSnapshot } from "firebase/firestore";

// 实时监听文档变化
function listenToDocument() {
  const docRef = doc(db, "collectionName", "documentId");
  
  const unsubscribe = onSnapshot(docRef, (doc) => {
    if (doc.exists()) {
      const data = doc.data(); // 将数据加载到变量中
      console.log("Current data:", data);
    } else {
      console.log("No such document!");
    }
  });
  
  // 返回取消监听函数，可以在组件卸载时调用
  return unsubscribe;
}

import { collection, getDocs } from "firebase/firestore";

// 获取集合中的所有文档
async function getCollectionData() {
  const querySnapshot = await getDocs(collection(db, "collectionName"));
  const dataArray = [];
  
  querySnapshot.forEach((doc) => {
    dataArray.push({
      id: doc.id,
      ...doc.data()
    });
  });
  
  console.log("Collection data:", dataArray);
  return dataArray;
}

// 确保使用async/await或.then()处理异步操作
async function getData() {
  const docRef = doc(db, "collection", "doc");
  const docSnap = await getDoc(docRef);
  
  if (docSnap.exists()) {
    return docSnap.data();
  }
  return null;
}

// React组件示例
useEffect(() => {
  const unsubscribe = onSnapshot(docRef, (doc) => {
    // 处理数据
  });
  
  return () => unsubscribe(); // 组件卸载时取消监听
}, []);

// 转换Timestamp为Date
import { Timestamp } from "firebase/firestore";

const data = docSnap.data();
if (data.timestamp instanceof Timestamp) {
  const date = data.timestamp.toDate();
  console.log(date);
}