Quick Start

Installation

npm

npm install -D universal-middleware @universal-middleware/core

yarn

yarn add -D universal-middleware @universal-middleware/core

pnpm

pnpm add -D universal-middleware @universal-middleware/core

bun

bun add -D universal-middleware @universal-middleware/core

Creating your first middleware

In this step, we will create a simple middleware that returns an early response if some header is missing.

IMPORTANT

All middleware files must include .middleware. in their name, and handlers .handler.. Without it, the bundler will not generate any adapter.

// src/middlewares/demo.middleware.ts

import type { Get, UniversalMiddleware } from "@universal-middleware/core";

interface Config {
  header: string;
}

// This middleware will return an early response if given header is missing
const guardMiddleware = ((config) => (request, ctx) => {
  if (!request.headers.has(config.header)) {
    return new Response("Header not present", {
      status: 401,
    });
  }
  // else we do nothing
  
  // Using `satisfies` to not lose return type
}) satisfies Get<[Config], UniversalMiddleware>;

// export default is mandatory
export default guardMiddleware;

Example of usage with Hono after packaging

After bundling, this middleware would be used as follows:

TIP

This is what your user facing documentation would contain.

import { Hono } from "hono";
// Once published as "some-lib"
import guardMiddleware from "some-lib/middlewares/demo-middleware-hono";

const app = new Hono();

app.use(guardMiddleware({ header: 'X-Universal-Demo' }));

export default app;