204 lines
14 KiB
Markdown
204 lines
14 KiB
Markdown
<img src="https://dl.dropboxusercontent.com/u/6396913/koa/logo.png" alt="koa middleware framework for nodejs" width="255px" />
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[![gitter][gitter-image]][gitter-url]
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[![NPM version][npm-image]][npm-url]
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[![build status][travis-image]][travis-url]
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[![Test coverage][coveralls-image]][coveralls-url]
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[![OpenCollective Backers][backers-image]](#backers)
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[![OpenCollective Sponsors][sponsors-image]](#sponsors)
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Expressive, light-weight HTTP framework for node.js to make web applications and APIs more enjoyable to write. Koa requests flow through middleware in a stack-like manner, allowing you to perform actions downstream then filter and manipulate the response upstream. Koa's use of generators also greatly increases the readability and robustness of your application.
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Only methods that are common to nearly all HTTP servers are integrated directly into Koa's small ~550 SLOC codebase. This
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includes things like content negotiation, normalization of node inconsistencies, redirection, and a few others.
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Koa is not bundled with any middleware, but there is a [large collection](https://github.com/koajs/koa/wiki) of community middleware to choose from.
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## Installation
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```
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$ npm install koa
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```
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Koa is supported in node v4+ and node v0.12 with the `--harmony-generators` or `--harmony` flag.
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## Koa v2
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Koa v2 is currently released with the `next` tag (meaning it will not be marked as latest).
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You can install it with semver:
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```bash
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npm install koa@2
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```
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In this new version, the middleware function signature completely changes in favor of ES2015-2016 syntax:
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```js
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// Koa application is now a class and requires the new operator.
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const app = new Koa();
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// uses async arrow functions
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app.use(async (ctx, next) => {
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try {
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await next(); // next is now a function
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} catch (err) {
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ctx.body = { message: err.message };
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ctx.status = err.status || 500;
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}
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});
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app.use(async ctx => {
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const user = await User.getById(ctx.session.userid); // await instead of yield
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ctx.body = user; // ctx instead of this
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});
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```
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Although deprecated, the older, generator-based middleware signature will still work in v2 via [koa-convert](https://github.com/koajs/convert) and will be removed in v3.
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To learn more about Koa v2, follow [this issue](https://github.com/koajs/koa/issues/533) or read the docs here: https://github.com/koajs/koa/tree/v2.x/docs.
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## Community
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- [API](docs/api/index.md) documentation
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- [Badgeboard](https://koajs.github.io/badgeboard) and list of official modules
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- [Examples](https://github.com/koajs/examples)
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- [Middleware](https://github.com/koajs/koa/wiki) list
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- [Wiki](https://github.com/koajs/koa/wiki)
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- [G+ Community](https://plus.google.com/communities/101845768320796750641)
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- [Reddit Community](https://www.reddit.com/r/koajs)
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- [Mailing list](https://groups.google.com/forum/#!forum/koajs)
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- [Guide](docs/guide.md)
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- [FAQ](docs/faq.md)
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- [中文文档](https://github.com/guo-yu/koa-guide)
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- __[#koajs]__ on freenode
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## Getting started
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- [Kick-Off-Koa](https://github.com/koajs/kick-off-koa) - An intro to koa via a set of self-guided workshops.
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- [Workshop](https://github.com/koajs/workshop) - A workshop to learn the basics of koa, Express' spiritual successor.
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- [Introduction Screencast](http://knowthen.com/episode-3-koajs-quickstart-guide/) - An introduction to installing and getting started with Koa
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## Example
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```js
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var koa = require('koa');
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var app = koa();
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// logger
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app.use(function *(next){
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var start = new Date;
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yield next;
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var ms = new Date - start;
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console.log('%s %s - %s', this.method, this.url, ms);
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});
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// response
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app.use(function *(){
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this.body = 'Hello World';
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});
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app.listen(3000);
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```
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## Running tests
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```
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$ make test
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```
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## Authors
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- [TJ Holowaychuk](https://github.com/tj)
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- [Jonathan Ong](https://github.com/jonathanong)
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- [Julian Gruber](https://github.com/juliangruber)
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- [Yiyu He](https://github.com/dead-horse)
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## Backers
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Support us with a monthly donation and help us continue our activities.
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<a href="https://opencollective.com/koajs/backer/0/website" target="_blank"><img src="https://opencollective.com/koajs/backer/0/avatar.svg"></a>
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<a href="https://opencollective.com/koajs/backer/1/website" target="_blank"><img src="https://opencollective.com/koajs/backer/1/avatar.svg"></a>
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## Sponsors
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Become a sponsor and get your logo on our README on Github with a link to your site.
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<a href="https://opencollective.com/koajs/sponsor/0/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/0/avatar.svg"></a>
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<a href="https://opencollective.com/koajs/sponsor/1/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/1/avatar.svg"></a>
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# License
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MIT
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[npm-image]: https://img.shields.io/npm/v/koa.svg?style=flat-square
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[npm-url]: https://www.npmjs.com/package/koa
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[travis-image]: https://img.shields.io/travis/koajs/koa/master.svg?style=flat-square
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[travis-url]: https://travis-ci.org/koajs/koa
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[coveralls-image]: https://img.shields.io/codecov/c/github/koajs/koa.svg?style=flat-square
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[coveralls-url]: https://codecov.io/github/koajs/koa?branch=master
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[backers-image]: https://opencollective.com/koajs/backers/badge.svg?style=flat-square
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[sponsors-image]: https://opencollective.com/koajs/sponsors/badge.svg?style=flat-square
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[gitter-image]: https://img.shields.io/gitter/room/koajs/koa.svg?style=flat-square
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[gitter-url]: https://gitter.im/koajs/koa?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge
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[#koajs]: https://webchat.freenode.net/?channels=#koajs
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