This library provides simple yet complete higher order function
with responsibility of composing multiple middleware functions into one Next.js API route handler.

The library does not contain routing utilities. I believe mechanism built in
Next.js itself or next-connect library are sufficient solutions.

• 😇 Simple and powerful API
• 🥷 TypeScript support
• 🧬 Maintaining order of middleware chain
• 🔧 Compatible with Express/Connect middleware
• 💢 Error handling
• 📦 No dependencies
• 💯 100% Test coverage

npm i next-api-compose -S
# or
yarn add next-api-compose

import { compose } from 'next-api-compose'

export default compose([withBar, withFoo], (request, response) => {
  const { foo, bar } = request
  response.status(200).json({ foo, bar })
})

the withBar middleware will append bar property to request object, then withFoo will do accordingly the same but with foo property

If you want to use next-api-compose along with Connect middleware that is widely used eg. in Express framework, there is special utility function for it.

import { compose, convert } from 'next-api-compose'
import helmet from 'helmet'

const withHelmet = convert(helmet())

export default compose([withBar, withFoo, withHelmet], (request, response) => {
  const { foo, bar } = request
  response.status(200).json({ foo, bar })
})

in this example, popular middleware helmet is converted using utility function from next-api-compose and passed as one element in middleware chain

You can find more examples here:

• JavaScript
  • Basic usage with error handling
  • Basic usage with Connect/Express middleware
• TypeScript
  • Basic usage with TypeScript
  • Advanced & complete usage with TypeScript

the example/ directory contains simple Next.js application implementing next-api-compose . To fully explore examples implemented in it by yourself - simply do cd examples && npm i && npm run dev then navigate to http://localhost:3000/

1. You may need to add

   export const config = {
     api: {
       externalResolver: true
     }
   }

   to your Next.js API route configuration in order to dismiss false positive about stalled API requests.
   Discussion about this can be found on the Next.js GitHub repository page.

2. If you are using TypeScript and strict types (no any at all), you may want to use Partial

   type NextApiRequestWithFoo = NextApiRequest & Partial<{ foo: string }>

   when extending API Route parameters' objects to avoid type errors during usage of compose.

This project is licensed under the MIT license.
All contributions are welcome.