Next.js: Metadata и SEO — пример кода

// app/blog/[slug]/page.tsx
import type { Metadata } from 'next';

// Dynamic metadata — fetch is DEDUPED with the page body's fetch
export async function generateMetadata(
  { params }: { params: Promise }
): Promise {
  const { slug } = await params;
  const post = await getPost(slug); // same call the page makes → one request

  return {
    title: post.title,                       // → "post.title · Acme" via template
    description: post.excerpt,
    alternates: { canonical: `/blog/${slug}` }, // canonical URL — dedupe signal
    openGraph: {
      title: post.title,
      images: [{ url: post.ogImage, width: 1200, height: 630 }],
      type: 'article',
    },
    twitter: { card: 'summary_large_image' },
  };
}

export default async function Page({ params }: { params: Promise }) {
  const { slug } = await params;
  const post = await getPost(slug); // deduped with the call above
  return {post.body};
}

// app/sitemap.ts — typed, dynamic sitemap generated at request/build time
import type { MetadataRoute } from 'next';
export default async function sitemap(): Promise {
  const posts = await getAllPosts();
  return posts.map((p) => ({
    url: `
    lastModified: p.updatedAt,
    changeFrequency: 'weekly',
    priority: 0.7,
  }));
}