投稿ページでserverTimestampを取得

PostPage.js

import { serverTimestamp } from "firebase/firestore";

const newPost = {
  uid: user.uid,
  text,
  createdAt: serverTimestamp(), // ← 追加（投稿日時）
  likes: 0,
  user: user.email,
  displayName: resolvedName,
  photoURL: resolvedPhoto,
  imageUrl,
  videoUrl,
  comments: [],
  draftComment: ''
};

投稿一覧取得時に「createdAt」で降順にソート

Home.js

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

const fetchPosts = async () => {
  try {
    const postsCollection = collection(db, "posts");
    const q = query(postsCollection, orderBy("createdAt", "desc"));  // ← ここで降順指定
    const snapshot = await getDocs(q);

    setDebugInfo(`Firestore投稿件数: ${snapshot.size} 件`);

    // 以降は同じコードでOK
    const postsData = await Promise.all(snapshot.docs.map(async (docSnap) => {
      //...
    }));

    setPosts(postsData);
    setDebugInfo(prev => prev + `\n読み込み成功: ${postsData.length} 件の投稿を取得`);
    setLoading(false);
  } catch (err) {
    setDebugInfo(`❌ 投稿取得エラー: ${err.message}`);
    console.error("Error getting posts:", err);
  }
};

UI