Fanl is an extremely simple and easy-to-use js server framework driven by the App Router file system routing.

Compatible with various js runtimes, such as Bun and Node.

bun add fanl
# or
npm i fanl
# or
pnpm add fanl

Use in Bun

Create the app directory

app
└── hello
    └── GET.ts

Edit GET.ts

export default (request: Request) => {
  return new Response("hello");
};

Create main.ts in the root directory

import { serve } from "bun";
import { createFanlFetch } from "fanl";

const fanlFetch = await createFanlFetch("./app");

serve({
  fetch: fanlFetch,
  port: 8080,
});

Use in Node

Step 1: Change *.ts to *.mjs in the above Bun code

Step 2: Import the Node compatibility layer.

Since Node's own HTTP Server API is not compatible with the Web standard Fetch API, a compatibility layer is needed. Fortunately, the Hono framework provides a Node compatibility layer hono/node-server, which is great.

Install @hono/node-server and modify main.mjs

import { serve } from "@hono/node-server";
import { createFanlFetch } from "fanl";

const fanlFetch = await createFanlFetch("./app");

serve({
  fetch: fanlFetch,
  port: 8080,
});

Run

bun run main.ts
# or
node main.mjs

Visit http://localhost:8080/hello

The App Router file system routing specification was first designed and popularized by NextJS, and its simple usage and excellent design provided the most direct inspiration for Fanl. Fanl chose to implement it as a route controller for pure server-side frameworks.

Define Routes

Each folder represents a route segment mapped to a URL segment. To create nested routes, you can nest folders within each other.

app
└── dashboard
    └── settings

Corresponding URLs

• /dashboard
• /dashboard/settings

Create Endpoints

Create a GET.ts interface file in the corresponding route directory.

app
└── dashboard
    ├── GET.ts
    └── settings
        └── GET.ts

GET.ts

export default (request: Request) => {
  return new Response("hello");
};

Request

Use fetch to request the interface in the browser.

const res = await fetch("/dashboard");
await res.text(); // hello

The App Router file system routing has three types of dynamic route segments

• [slug]
• [...slug]
• [[...slug]]

app
├── roles
│   └── [id]
│       └── [name]
├── posts
│   └── [[...ids]]
└── users
    └── [...ids]

Corresponding URLs, routes, and parameter matching table

Get Params in the interface

import { useContext, useParams } from "fanl";

export default (request: Request) => {
  const ctx = useContext(); // ctx.params;
  const params = useParams<T>(); // equivalent to useContext().params
  return new Response("hello");
};

Wildcard Routes

[[...ids]] and [...ids] can capture the remaining route segments and can only be placed at the deepest level of the directory.

The difference between the two is that the former is optional, and the latter is required. An optional segment can match exhausted URL segments, as seen in the matching routes for the URLs /user and /posts in the table above.

File name: %METHOD%.ts

The implementation file for the interface, which needs to export a default processing function, where %METHOD% is all http protocol methods.

export default (request: Request) => {
  // request.method -> "get" "post" ...
  return new Response("hello");
};

File name: handler.ts

When a route has multiple interface implementations, all methods can be placed in the handler, and the handler supports fallback processing.

export const GET = () => {
  return new Response("GET");
};

export const POST = () => {
  return new Response("POST");
};

// Fallback
export default () => {
  return new Response("ALL");
};

Priority

When the interface file and the composite interface define the same interface method, the interface file takes precedence. If neither is defined, the fallback file in the composite interface is used.

| Object | Priority | | ----------------------- | ------ | | Interface file | High | | Interface exported by composite interface file | Medium | | Default export of composite interface file | Low |

The implementation of middleware is similar to koa, using the onion ring model.

app
├── middleware.ts #1
└── roles
    ├── middleware.ts #2
    └── [id]
        ├── GET.ts
        └── middleware.ts #3

Assuming the above middleware is a simple log middleware, as follows:

export default (
  request: Request,
  next: (req: Request) => Promise<Response>
) => {
  console.log("request #x");
  const res = await next(request);
  console.log("response  #x");
  return res;
};

Execution order of middleware for the request /roles/a

request #1
  request #2
    request #3
      get
    response #3
  response #2
response #1

When a route has multiple middleware, you can use the compose method to combine them.

import { compose } from "fanl";

export default compose(middleware1, middleware2, middleware3);