Next.js: Route handlers (API) — пример кода

// app/api/posts/[id]/route.ts
import { NextRequest, NextResponse } from 'next/server';

export async function GET(
  req: NextRequest,
  { params }: { params: Promise },
) {
  const { id } = await params;                    // Next 15: async params
  const q = req.nextUrl.searchParams.get('fields'); // query string
  const post = await db.post.find(id);
  if (!post) return new NextResponse('Not found', { status: 404 });
  return NextResponse.json(post);
}

// Streaming a response with a ReadableStream (e.g. LLM tokens, SSE)
export async function GET() {
  const stream = new ReadableStream({
    async start(controller) {
      for (const chunk of await source()) controller.enqueue(chunk);
      controller.close();
    },
  });
  return new Response(stream, { headers: { 'Content-Type': 'text/event-stream' } });
}

// Setting cookies on the response
export async function POST() {
  const res = NextResponse.json({ ok: true });
  res.cookies.set('session', token, { httpOnly: true, secure: true, sameSite: 'lax' });
  return res;
}