acorn

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

Usage

Under Deno runtime or Deploy

Add the package to your project:

deno add @oak/acorn

Under Node.js and Cloudflare Workers

Install the package using your chosen package manager:

npm

npx jsr add @oak/acorn

Yarn

yarn dlx jsr add @oak/acorn

pnpm

pnpm dlx jsr add @oak/acorn

Under Bun

bunx jsr add @oak/acorn

Listening

For Deno, Node.js, and Bun the router needs to be configured and then start listening for requests:

import { Router } from "@oak/acorn";

const BOOKS = {
  "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 });

Fetch handlers

For Cloudflare Workers the router needs to be configured and the router’s fetch handler needs to be exported:

import { Router } from "@oak/acorn";

const BOOKS = {
  "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 });

export default { fetch: router.fetch };

Philosophy

After having spent years working on oak and extensive experience with building Deno, that really when people were looking at middleware type of solution, really what they were looking fore was a straight forward router that made it easy to handle JSON payloads.

Also, oak was created in the early days of Deno, before it even had a native HTTP server, and that server supported the web standard Request and Response.

Acorn was the culmination of that need. It makes it easy to have route handlers that are straight forward and focuses on staying closer to the native implementations of Deno constructs that have evolved over time.

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 addr: Addr;
  readonly cookies: SecureCookieMap;
  readonly params: Params;
  readonly request: Request;
  readonly searchParams: Record<string, string>;
  body(): Promise<BodyType | undefined>;
  url(): URL;
}

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

The .searchParams property provides any search parameters associated with the request.

The .addr property provides the remote address associated with the request.

The .url() method returns an instance of URL associated with the request.

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.