How can I pass values between koa-router routes

Question

I wanted to move the authentication procedure from all routes into one route (koa-router provides the all() middleware for all methods on a router for this). However, in the process, I decode a token whose decoding I need for further execution. How can I access this decoded token from another route?

const Router = require('koa-router');
const router = new Router({ prefix: '/test' });

router.all('/', async (ctx, next) => {
   //decode
   await next();
})

router.get('/', async ctx=> {
   // Here I need to access decoded, too
});

Answer 1

the Koa Context object encapsulates the request, response and a state object, along with much more. This state object is the recommended namespace where you can pass data between middleware.

Modifiying the provided example gets:

const http = require('http')
const Koa = require('koa')
const Router = require('koa-router')
const app = new Koa()
const router = new Router({ prefix: '/test' })

router.all('/', async (ctx, next) => {
    // decode token
    const x = 'foo'
    // assign decoded token to ctx.state
    ctx.state.token = x
    await next()
 })

 router.get('/', async ctx=> {
    // access ctx.state
    console.log(ctx.state.token)
 })

 app.use(router.routes())
http.createServer(app.callback()).listen(3000)

Navigate to http://localhost:3000/test and see the decoded token logged to the console.