Route handlers (APIs)

Export a function per HTTP method

import { getDishes } from "@/lib/data";

export async function GET(request) {
  const veg = request.nextUrl.searchParams.get("veg");
  const dishes = await getDishes();
  const list = veg === "true" ? dishes.filter((d) => d.veg) : dishes;
  return Response.json(list.map((d) => ({ slug: d.slug, name: d.name, price: d.price })));
}

export async function POST(request) {
  const body = await request.json();
  if (!body.name) {
    return Response.json({ error: "name is required" }, { status: 400 });
  }
  return Response.json({ ok: true, name: body.name }, { status: 201 });
}

• Dynamic segments work here too: app/api/dishes/[slug]/route.js receives { params } as the second argument.
• A folder can have page.jsx or route.js, not both.
• Your own pages usually don't need an API: Server Components can read data directly. Route handlers are for *other* clients.