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.
constKoa=require('koa');constc2k=require('koa-connect');// A generic Express-style middleware functionfunctionconnectMiddlware(req,res,next){res.writeHead(200,{'Content-Type': 'text/plain'});res.end('From the Connect middleware');next();}// A generic Koa middlware, without async/awaitfunctionkoaMiddlware(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/awaitasyncfunctionkoaMiddleware(ctx,next){try{awaitnext();}catch(e){// Normal error handling}// Normal control flow}constapp=newKoa();app.use(koaMiddlware);app.use(c2k(connectMiddlware));app.use((ctx,next)=>{console.log('It will continue on to here');});app.listen(3000);
Contributing
Developing
npm start starts the TypeScript compiler in watch mode. Code will be auto-formatted upon commit as part of the Prettier + lint-staged + Husky setup.
Building
npm run build produces the types declaration file and JavaScript file for publishing.
Testing
npm test runs the tests. Tests are in tests.js and are made with the Mocha framework.
Use npm run test:watch in conjunction with npm start to automatically re-run the tests when the source changes.
请发表评论