Koam

Implement a simple Koa-like http server with zero dependencies from scratch.

THIS FRAMEWORK HAVE NOT BEEN STRICTLY TESTED, PLEASE DO NOT USE IT IN PRODUCTION ! 许多功能未经严格测试，请勿用于生产目的！

Advantage

• Lightweight (0 dependency)
• TypeScript friendly
• Built-in body parser middleware
• Built-in response time middleware

Sub-package

If you're looking for the ultimate in minimal packages and high customization, you can install the following subpackages separately. Of course, they are all included in the main package (@mutoe/koam).

• Koam core package @mutoe/koam-core
• Router middleware @mutoe/koam-router
• Logger middleware @mutoe/koam-logger

Usage

import Koa from '@mutoe/koam'
import Router from '@mutoe/koam-router'

const app = new Koa()
const router = new Router()

router.post('/hello/:name', ctx => {
  console.log(ctx.request.body) // You can get json request body directly
  ctx.body = `Hello ${ctx.params.name}!`
})

app.use(router.routes())
app.listen(3000, () => console.log(`server is started at 3000...`))

Notes

1. ctx.assert mast explicit declare context type

See microsoft/Typescript#34523

app.use(async (ctx: Context, next) => {
  //                ^^^^^^^
  const val: unknown = 1.2345
  //         ^^^^^^^
  ctx.assert(typeof val === 'number', 500)
  console.log(val.toFixed(2))
  //          ^^^ now val is number type
})

2. Extend type

If you want to extend some property or method on the context or it's state, you can write the following code to extend it

// extend.d.ts
import User from './src/user'
declare global {
  namespace Koa {
    export interface State {
      user?: User
    }
  }
}
export {}

// your-code.ts
app.use(ctx => {
  console.log(ctx.state.user.name)
})

You can refer the koam-router extend-koam.d.ts for more example.

3. Cookie

In order to reduce the package size, I don't have built-in cookie-related handling, as this is not required by all apps.

If you want to handle cookies, you can extend the middleware yourself, here is the cookies example steps:

1. install the cookies and @types/cookies npm package

2. add koam.d.ts in your app

   import '@mutoe/koam'
   import type Cookies from 'cookies'
   
   declare module '@mutoe/koam' {
     interface Context {
       cookies: Cookies
     }
   }
   
   declare global {
     namespace Koa {
       // Others if you want extend
       interface State {
         user?: { id: number, email: string }
       }
     }
   
   }
   
   // Don't forgot this line
   export {}

3. register the cookies in your app

   const app = new Koa()
   // init cookies before your middleware
   app.use((ctx, next) => {
     ctx.cookies = new Cookies(ctx.req, ctx.res, { secure: true })
     return next()
   })
   
   // your middlewares
   app.use(ctx => {
     ctx.cookies.set('key', 'value')
     ctx.cookies.get('key')
   })

4. Body Parser

The json body parser middleware is built-in, you can get the parsed body directly from ctx.request.body.

But if you want to parse other types of body (like multipart/form-data), you can close built-in body parser and use the another middleware like formidable

1. install the formidable and @types/formidable npm package

2. add koam.d.ts in your app

   import '@mutoe/koam'
   import type Cookies from 'cookies'
   
   declare module '@mutoe/koam' {
     interface Context {
       body?: any
       files?: formidable.File[]
     }
     interface Request {
       body?: any
       files?: formidable.File[]
     }
   }
   
   // Don't forgot this line
   export {}

3. register the formidable in your app

   import { Fields, Files, formidable } from 'formidable'
   const app = new Koa({
     customBodyParser: false, // this is not nessary, but it's better for performance
   })
   app.use(async (ctx, next) => {
     const form = formidable()
     try {
       const [fields, files] = await form.parse(ctx.req)
       ctx.request.body = fields
       ctx.request.files = files
     }
     catch (error) {
       console.error('Cannot parse the request body', { error })
     }
     await next()
   })
   
   app.use(ctx => {
     console.log(ctx.request.body as Fields)
     console.log(ctx.files as Files)
   })