throwback

Throwback

Simple asynchronous middleware pattern.

Installation

npm install throwback --save

Usage

Compose asynchronous (promise-returning) functions.

const { compose } = require('throwback')

const fn = compose([
  async function (ctx, next) {
    console.log(1)

    try {
      await next()
    } catch (err) {
      console.log('throwback', err)
    }

    console.log(4)
  },
  async function (ctx, next) {
    console.log(2)

    return next()
  }
])

// Callback runs at the end of the stack, before
// the middleware bubbles back to the beginning.
fn({}, function (ctx) {
  console.log(3)

  ctx.status = 404
})

Tip: In development mode, debug mode will throw errors when you do something unexpected. In production, faster non-error code paths are used.

Example

Build a micro HTTP server!

const { createServer } = require('http')
const finalhandler = require('finalhandler') // Example only, not compatible with single `ctx` arg.
const { compose } = require('throwback')

const app = compose([
  function ({ req, res }, next) {
    res.end('Hello world!')
  }
])

createServer(function (req, res) {
  return app({ req, res }, finalhandler())
}).listen(3000)

Use Cases

• HTTP requests (e.g. popsicle)
• HTTP servers (e.g. servie)
• Processing pipelines (e.g. scrappy)

Inspiration

Built for servie and inspired by koa-compose.

License

MIT