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# koa-connect [![npm package badge][npm badge]][npm]
[npm badge]: https://badge.fury.io/js/koa-connect.svg
[npm]: https://www.npmjs.com/package/koa-connect
Use [Express](https://github.com/strongloop/express)/[Connect](https://github.com/senchalabs/connect) middleware with [Koa](https://github.com/koajs/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` 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`.
## Installation
```sh
npm install koa-connect
```
## Usage
See [`examples/`](./examples) for more practical usage.
```javascript
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')
next()
}
// A generic Koa middlware, without async/await
function koaMiddlware(ctx, next) {
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(koaMiddlware)
app.use(c2k(connectMiddlware))
app.use((ctx, next) => {
console.log('It will continue on to here')
})
app.listen(3000)
```
## Testing
Tests are in `tests.js` and are made with the [Mocha](https://mochajs.org) framework. You can run them with `npm test` or `npm run test:watch`
## License
MIT
|
