koa2-connect

Base on koa-connect, improve to support webpack-dev-middleware and webpack-hot-middleware. Use Express/Connect middleware with Koa.

Warning

It is highly recommended to use a Koa-specific middleware instead of trying to convert an Express version when they're available. There is a non-trivial difference in the Koa and Express designs and you will inevitably run into some issues. This module is a workaround for the specific cases where the differences can be ignored. Additionally, it also enables library authors to write 1 version of their HTTP middleware.

Always use next

Express middlewares need to declare and invoke the next callback appropriately for the koa-connect integration to work correctly.

For library authors

If you're attempting to write a framework-agnostic middleware library, be sure to use only core HTTP methods and not any Express-dependent APIs like res.send.

Installation

1npm install koa2-connect

Usage

See examples/ for more real-world examples.

1const Koa = require('koa')
2const c2k = require('koa2-connect')
3
4// A generic Express-style middleware function
5function connectMiddlware (req, res, next) {
6  res.writeHead(200, {'Content-Type': 'text/plain'})
7  res.end('From the Connect middleware')
8  next()
9}
10
11// A generic Koa v2 middlware, without async/await
12function koaMiddlware(ctx, next) {
13  return next()
14    .then(() => {
15      // The control flow will bubble back to here, like usual
16    })
17    .catch((err) => {
18      // Error handling from downstream middleware, like usual
19    })
20}
21
22// A generic Koa v2 middlware with async/await
23async function koaMiddleware(ctx, next) {
24  try {
25    await next();
26  } catch (e) {
27    // Normal error handling
28  }
29  // Normal control flow
30}
31
32const app = new Koa()
33app.use(koaMiddlware)
34app.use(c2k(connectMiddlware))
35app.use((ctx, next) => {
36  console.log('It will continue on to here')
37})
38
39app.listen(3000)

Testing

Tests are in tests.js and are made with the Mocha framework. You can run them with npm test or npm run test:watch

License

MIT