303 lines
16 KiB
Markdown
303 lines
16 KiB
Markdown
<img src="https://dl.dropboxusercontent.com/u/6396913/koa/logo.png" alt="koa middleware framework for nodejs" width="255px" />
|
|
|
|
[![gitter][gitter-image]][gitter-url]
|
|
[![NPM version][npm-image]][npm-url]
|
|
[![build status][travis-image]][travis-url]
|
|
[![Test coverage][coveralls-image]][coveralls-url]
|
|
[![OpenCollective Backers][backers-image]](#backers)
|
|
[![OpenCollective Sponsors][sponsors-image]](#sponsors)
|
|
|
|
Expressive HTTP middleware framework for node.js to make web applications and APIs more enjoyable to write. Koa's middleware stack flows in a stack-like manner, allowing you to perform actions downstream then filter and manipulate the response upstream.
|
|
|
|
Only methods that are common to nearly all HTTP servers are integrated directly into Koa's small ~570 SLOC codebase. This
|
|
includes things like content negotiation, normalization of node inconsistencies, redirection, and a few others.
|
|
|
|
Koa is not bundled with any middleware.
|
|
|
|
## Installation
|
|
|
|
Koa requires __node v7.6.0__ or higher for ES2015 and async function support.
|
|
|
|
```
|
|
$ npm install koa
|
|
```
|
|
|
|
## Hello koa
|
|
|
|
```js
|
|
const Koa = require('koa');
|
|
const app = new Koa();
|
|
|
|
// response
|
|
app.use(ctx => {
|
|
ctx.body = 'Hello Koa';
|
|
});
|
|
|
|
app.listen(3000);
|
|
```
|
|
|
|
## Getting started
|
|
|
|
- [Kick-Off-Koa](https://github.com/koajs/kick-off-koa) - An intro to koa via a set of self-guided workshops.
|
|
- [Workshop](https://github.com/koajs/workshop) - A workshop to learn the basics of koa, Express' spiritual successor.
|
|
- [Introduction Screencast](http://knowthen.com/episode-3-koajs-quickstart-guide/) - An introduction to installing and getting started with Koa
|
|
|
|
|
|
## Middleware
|
|
|
|
Koa is a middleware framework that can take two different kinds of functions as middleware:
|
|
|
|
* async function
|
|
* common function
|
|
|
|
Here is an example of logger middleware with each of the different functions:
|
|
|
|
### ___async___ functions (node v7.6+)
|
|
|
|
```js
|
|
app.use(async (ctx, next) => {
|
|
const start = new Date();
|
|
await next();
|
|
const ms = new Date() - start;
|
|
console.log(`${ctx.method} ${ctx.url} - ${ms}ms`);
|
|
});
|
|
```
|
|
|
|
### Common function
|
|
|
|
```js
|
|
// Middleware normally takes two parameters (ctx, next), ctx is the context for one request,
|
|
// next is a function that is invoked to execute the downstream middleware. It returns a Promise with a then function for running code after completion.
|
|
|
|
app.use((ctx, next) => {
|
|
const start = new Date();
|
|
return next().then(() => {
|
|
const ms = new Date() - start;
|
|
console.log(`${ctx.method} ${ctx.url} - ${ms}ms`);
|
|
});
|
|
});
|
|
```
|
|
|
|
### Koa v1.x Middleware Signature
|
|
|
|
The middleware signature changed between v1.x and v2.x. The older signature is deprecated.
|
|
|
|
**Old signature middleware support will be removed in v3**
|
|
|
|
Please see the [Migration Guide](docs/migration.md) for more information on upgrading from v1.x and
|
|
using v1.x middleware with v2.x.
|
|
|
|
## Context, Request and Response
|
|
|
|
Each middleware receives a Koa `Context` object that encapsulates an incoming
|
|
http message and the corresponding response to that message. `ctx` is often used
|
|
as the parameter name for the context object.
|
|
|
|
```js
|
|
app.use(async (ctx, next) => { await next(); });
|
|
```
|
|
|
|
Koa provides a `Request` object as the `request` property of the `Context`.
|
|
Koa's `Request` object provides helpful methods for working with
|
|
http requests which delegate to an [IncomingMessage](https://nodejs.org/api/http.html#http_class_http_incomingmessage)
|
|
from the node `http` module.
|
|
|
|
Here is an example of checking that a requesting client supports xml.
|
|
|
|
```js
|
|
app.use(async (ctx, next) => {
|
|
ctx.assert(ctx.request.accepts('xml'), 406);
|
|
// equivalent to:
|
|
// if (!ctx.request.accepts('xml')) ctx.throw(406);
|
|
await next();
|
|
});
|
|
```
|
|
|
|
Koa provides a `Response` object as the `response` property of the `Context`.
|
|
Koa's `Response` object provides helpful methods for working with
|
|
http responses which delegate to a [ServerResponse](https://nodejs.org/api/http.html#http_class_http_serverresponse)
|
|
.
|
|
|
|
Koa's pattern of delegating to Node's request and response objects rather than extending them
|
|
provides a cleaner interface and reduces conflicts between different middleware and with Node
|
|
itself as well as providing better support for stream handling. The `IncomingMessage` can still be
|
|
directly accessed as the `req` property on the `Context` and `ServerResponse` can be directly
|
|
accessed as the `res` property on the `Context`.
|
|
|
|
Here is an example using Koa's `Response` object to stream a file as the response body.
|
|
|
|
```js
|
|
app.use(async (ctx, next) => {
|
|
await next();
|
|
ctx.response.type = 'xml';
|
|
ctx.response.body = fs.createReadStream('really_large.xml');
|
|
});
|
|
```
|
|
|
|
The `Context` object also provides shortcuts for methods on its `request` and `response`. In the prior
|
|
examples, `ctx.type` can be used instead of `ctx.request.type` and `ctx.accepts` can be used
|
|
instead of `ctx.request.accepts`.
|
|
|
|
For more information on `Request`, `Response` and `Context`, see the [Request API Reference](docs/api/request.md),
|
|
[Response API Reference](docs/api/response.md) and [Context API Reference](docs/api/context.md).
|
|
|
|
## Koa Application
|
|
|
|
The object created when executing `new Koa()` is known as the Koa application object.
|
|
|
|
The application object is Koa's interface with node's http server and handles the registration
|
|
of middleware, dispatching to the middleware from http, default error handling, as well as
|
|
configuration of the context, request and response objects.
|
|
|
|
Learn more about the application object in the [Application API Reference](docs/api/index.md).
|
|
|
|
## Documentation
|
|
|
|
- [Usage Guide](docs/guide.md)
|
|
- [Error Handling](docs/error-handling.md)
|
|
- [Koa for Express Users](docs/koa-vs-express.md)
|
|
- [FAQ](docs/faq.md)
|
|
- [API documentation](docs/api/index.md)
|
|
|
|
## Babel setup
|
|
|
|
If you're not using `node v7.6+`, we recommend setting up `babel` with [`babel-preset-env`](https://github.com/babel/babel-preset-env):
|
|
|
|
```bash
|
|
$ npm install babel-register babel-preset-env --save
|
|
```
|
|
|
|
Setup `babel-register` in your entry file:
|
|
|
|
```js
|
|
require('babel-register');
|
|
```
|
|
|
|
And have your `.babelrc` setup:
|
|
|
|
```json
|
|
{
|
|
"presets": [
|
|
["env", {
|
|
"targets": {
|
|
"node": true
|
|
}
|
|
}]
|
|
]
|
|
}
|
|
```
|
|
|
|
## Troubleshooting
|
|
|
|
Check the [Troubleshooting Guide](docs/troubleshooting.md) or [Debugging Koa](docs/guide.md#debugging-koa) in
|
|
the general Koa guide.
|
|
|
|
## Running tests
|
|
|
|
```
|
|
$ make test
|
|
```
|
|
|
|
## Authors
|
|
|
|
See [AUTHORS](AUTHORS).
|
|
|
|
## Community
|
|
|
|
- [Badgeboard](https://koajs.github.io/badgeboard) and list of official modules
|
|
- [Examples](https://github.com/koajs/examples)
|
|
- [Middleware](https://github.com/koajs/koa/wiki) list
|
|
- [Wiki](https://github.com/koajs/koa/wiki)
|
|
- [G+ Community](https://plus.google.com/communities/101845768320796750641)
|
|
- [Reddit Community](https://www.reddit.com/r/koajs)
|
|
- [Mailing list](https://groups.google.com/forum/#!forum/koajs)
|
|
- [中文文档](https://github.com/guo-yu/koa-guide)
|
|
- __[#koajs]__ on freenode
|
|
|
|
## Backers
|
|
|
|
Support us with a monthly donation and help us continue our activities.
|
|
|
|
<a href="https://opencollective.com/koajs/backer/0/website" target="_blank"><img src="https://opencollective.com/koajs/backer/0/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/1/website" target="_blank"><img src="https://opencollective.com/koajs/backer/1/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/2/website" target="_blank"><img src="https://opencollective.com/koajs/backer/2/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/3/website" target="_blank"><img src="https://opencollective.com/koajs/backer/3/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/4/website" target="_blank"><img src="https://opencollective.com/koajs/backer/4/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/5/website" target="_blank"><img src="https://opencollective.com/koajs/backer/5/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/6/website" target="_blank"><img src="https://opencollective.com/koajs/backer/6/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/7/website" target="_blank"><img src="https://opencollective.com/koajs/backer/7/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/8/website" target="_blank"><img src="https://opencollective.com/koajs/backer/8/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/9/website" target="_blank"><img src="https://opencollective.com/koajs/backer/9/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/10/website" target="_blank"><img src="https://opencollective.com/koajs/backer/10/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/11/website" target="_blank"><img src="https://opencollective.com/koajs/backer/11/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/12/website" target="_blank"><img src="https://opencollective.com/koajs/backer/12/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/13/website" target="_blank"><img src="https://opencollective.com/koajs/backer/13/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/14/website" target="_blank"><img src="https://opencollective.com/koajs/backer/14/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/15/website" target="_blank"><img src="https://opencollective.com/koajs/backer/15/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/16/website" target="_blank"><img src="https://opencollective.com/koajs/backer/16/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/17/website" target="_blank"><img src="https://opencollective.com/koajs/backer/17/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/18/website" target="_blank"><img src="https://opencollective.com/koajs/backer/18/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/19/website" target="_blank"><img src="https://opencollective.com/koajs/backer/19/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/20/website" target="_blank"><img src="https://opencollective.com/koajs/backer/20/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/21/website" target="_blank"><img src="https://opencollective.com/koajs/backer/21/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/22/website" target="_blank"><img src="https://opencollective.com/koajs/backer/22/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/23/website" target="_blank"><img src="https://opencollective.com/koajs/backer/23/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/24/website" target="_blank"><img src="https://opencollective.com/koajs/backer/24/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/25/website" target="_blank"><img src="https://opencollective.com/koajs/backer/25/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/26/website" target="_blank"><img src="https://opencollective.com/koajs/backer/26/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/27/website" target="_blank"><img src="https://opencollective.com/koajs/backer/27/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/28/website" target="_blank"><img src="https://opencollective.com/koajs/backer/28/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/backer/29/website" target="_blank"><img src="https://opencollective.com/koajs/backer/29/avatar.svg"></a>
|
|
|
|
|
|
## Sponsors
|
|
|
|
Become a sponsor and get your logo on our README on Github with a link to your site.
|
|
|
|
<a href="https://opencollective.com/koajs/sponsor/0/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/0/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/1/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/1/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/2/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/2/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/3/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/3/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/4/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/4/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/5/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/5/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/6/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/6/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/7/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/7/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/8/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/8/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/9/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/9/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/10/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/10/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/11/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/11/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/12/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/12/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/13/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/13/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/14/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/14/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/15/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/15/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/16/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/16/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/17/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/17/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/18/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/18/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/19/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/19/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/20/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/20/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/21/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/21/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/22/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/22/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/23/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/23/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/24/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/24/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/25/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/25/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/26/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/26/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/27/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/27/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/28/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/28/avatar.svg"></a>
|
|
<a href="https://opencollective.com/koajs/sponsor/29/website" target="_blank"><img src="https://opencollective.com/koajs/sponsor/29/avatar.svg"></a>
|
|
|
|
# License
|
|
|
|
MIT
|
|
|
|
[npm-image]: https://img.shields.io/npm/v/koa.svg?style=flat-square
|
|
[npm-url]: https://www.npmjs.com/package/koa
|
|
[travis-image]: https://img.shields.io/travis/koajs/koa/master.svg?style=flat-square
|
|
[travis-url]: https://travis-ci.org/koajs/koa
|
|
[coveralls-image]: https://img.shields.io/codecov/c/github/koajs/koa.svg?style=flat-square
|
|
[coveralls-url]: https://codecov.io/github/koajs/koa?branch=master
|
|
[backers-image]: https://opencollective.com/koajs/backers/badge.svg?style=flat-square
|
|
[sponsors-image]: https://opencollective.com/koajs/sponsors/badge.svg?style=flat-square
|
|
[gitter-image]: https://img.shields.io/gitter/room/koajs/koa.svg?style=flat-square
|
|
[gitter-url]: https://gitter.im/koajs/koa?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge
|
|
[#koajs]: https://webchat.freenode.net/?channels=#koajs
|