acorn

Rapidly develop and iterate on RESTful APIs using a strongly typed router designed for Deno CLI and Deno Deploy.

import { Router } from "https://deno.land/x/acorn/mod.ts";

const BOOKS: Record<string, { id: number; title: string }> = {
  "1": { id: 1, title: "The Hound of the Baskervilles" },
  "2": { id: 2, title: "It" },
};

const router = new Router();

router.get("/", () => ({ hello: "world" }));
router.get("/books/:id", (ctx) => BOOKS[ctx.params.id]);

router.listen({ port: 5000 });

Routes

An instance of a router has several methods for registering a handler for a route. The methods correspond to one or many HTTP methods or verbs. When a request is handled by the router that matches a route and the HTTP method(s), it will invoke the registered handler.

The handler is provided with a context which contains information about the request:

interface Context<Params extends Record<string, string>, BodyType> {
  readonly request: Request;
  readonly params: Params;
  body(): Promise<BodyType | undefined>;
}

The .params property provides any parameters (named captures) parsed out when matching the route string.

The .body() method is a convenience method to deal with decoding a JSON string body. It can be used with an optional deserializer which can do advanced decoding of the body, or it will attempted to be decoded from the JSON string.

More advanced request body handling can be handled via the .request property.

The handler is then expected to have a return value which can be a Request instance, a value that is a BodyInit, or any other value. If an optional serializer is provided and the response is not a Request instance or of the type BodyInit, the value will be passed to the serializer. If no serializer is present then JSON.stringify() will be used to attempt to convert the value to a JSON string. If undefined is returned, then a 404 NotFound response will be generated.

The handling of the request differs significantly from middleware solutions like oak. In most cases you will want only one handler per route and HTTP method combination. There is nothing that prevents multiple registrations, but the first handler registered that returns a non undefined value will be used and any remaining handlers will not be called.

Underneath, the router matches route strings using the browser standard URL Pattern API and matches the pathname part of the URL.