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Use connect and express middleware in koa
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Latest commit 99f40fc Jun 13, 2018

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Use Express/Connect middleware with Koa.


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 middleware parameter

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.


npm install koa-connect


See examples/ for more practical usage.

const Koa = require('koa')
const c2k = require('koa-connect')

// A generic Express-style middleware function
function connectMiddlware(req, res, next) {
  res.writeHead(200, { 'Content-Type': 'text/plain' })
  res.end('From the Connect middleware')

// A generic Koa middlware, without async/await
function koaMiddlware(ctx, next) {
    .then(() => {
      // The control flow will bubble back to here, like usual
    .catch(err => {
      // Error handling from downstream middleware, like usual

// A generic Koa middlware with async/await
async function koaMiddleware(ctx, next) {
  try {
    await next()
  } catch (e) {
    // Normal error handling
  // Normal control flow

const app = new Koa()
app.use((ctx, next) => {
  console.log('It will continue on to here')



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



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