Node Koa How do I pass a param into middleware?

Question

Converting my Express app to Koa...

I'm googling and I'm googling, I can't find how to pass extra params into Koa middleware. For example...

router.post('/', compose([
    Midware.verifyAuthToken, 
    Midware.bodySchemaTest(UserController.bodyAttribs),
    Midware.injectionTest
]), UserController.postNew);

I need send some variable bodyAttribs (string array) names into the bodySchemaTest middleware and I don't know how to do this in Koa.

I'm just now trying Koa. Please share your expertise :-)

Answer 1

Ok I worked it out myself. Not sure if this is smart or the "right" way to do this but the solution for me was to create a piece of middleware in each controller that sets expected schema attribs in ctx.state.bodyAttribs.

Like this...

// /src/routers/user.router.ts

import * as UserController from '../controller/user.controller';
import * as Midware from './middleware';
import Router from 'koa-router';
import compose from 'koa-compose';

const router = new Router();
router.prefix('/user');

router.get('/', Midware.verifyAuthToken, UserController.getAll);

router.post('/', compose([
    UserController.bodyAttribs,
    Midware.verifyAuthToken,
    Midware.bodySchemaTest,
    Midware.injectionTest,
]), UserController.postNew);

module.exports = router;


// /src/controller/user.controller.ts 

import { Context } from 'koa';
import { UserData } from '../data/mongo/user.data.mongo';
import { UserModel } from '../model/user.model';
import { EmailValidate } from '../service/email-validate.service';
import * as Logger from '../util/logger';

const dataContext = new UserData();

// Middleware to set bodyAttribs
export const bodyAttribs = async (ctx: Context, next: any) => {
    ctx.state.bodyAttribs = ['handle', 'processUserOptions', 'name', 'email', 'pass', 'passConfirm'];
    return await next();
};
...

So each controller provides the custom middleware that set the custom bodyAttribs I want to verify. You can use this approach to set and pass 1 to any number of extra params, whatever you need, in ctx.state which always goes on to next middleware in chain. Follow? :-)