ISR Incremental Static Regeneration Use incremental static regeneration (ISR) to rebuild pages on the fly

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Main Post Content Page

This page is statically generated, BUT regenerated after new requests come in at an interval of 5000ms. If a prerendered page does not exist, will fallback to regular SSR.

file_type_js_official pages/username/slug.js
import styles from '../../styles/Post.module.css';
import PostContent from '../../components/PostContent';
import { firestore, getUserWithUsername, postToJSON } from '../../lib/firebase';
import { useDocumentData } from 'react-firebase-hooks/firestore';

export async function getStaticProps({ params }) {
  const { username, slug } = params;
  const userDoc = await getUserWithUsername(username);

  let post;
  let path;

  if (userDoc) {
    const postRef = userDoc.ref.collection('posts').doc(slug);
    post = postToJSON(await postRef.get());

    path = postRef.path;

  return {
    props: { post, path },
    revalidate: 5000,

export async function getStaticPaths() {
  // Improve my using Admin SDK to select empty docs
  const snapshot = await firestore.collectionGroup('posts').get();

  const paths = => {
    const { slug, username } =;
    return {
      params: { username, slug },

  return {
    // must be in this format:
    // paths: [
    //   { params: { username, slug }}
    // ],
    fallback: 'blocking',

export default function Post(props) {

  return (
    <main className={styles.container}>


Post Content with Markdown

command line
npm i react-markdown

Learn more about React Markdown

file_type_js_official components/PostContent.js
import Link from 'next/link';
import ReactMarkdown from 'react-markdown';

// UI component for main post content
export default function PostContent({ post }) {
  const createdAt = typeof post?.createdAt === 'number' ? new Date(post.createdAt) : post.createdAt.toDate();

  return (
    <div className="card">
      <span className="text-sm">
        Written by{' '}
        <Link href={`/${post.username}/`}>
          <a className="text-info">@{post.username}</a>
        </Link>{' '}
        on {createdAt.toISOString()}


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