add middleware function to an async export - express

Question

I have separated my routes with their definitions so that my routes look like this:
const router = require('express').Router();
const handle = require('../handlers');
router.post('/register', handle.register);
// The handler defines the route. Like this:
exports.register = async (req, res, next) => {
try {
const user = await db.User.create(req.body);
const {id, username} = user;
res.status(201).json({id, username});
} catch (err) {
if(err.code === 11000){
err.message ='Sorry, details already taken';
}
next(err);
}
};
This works fine. Now I need to upload images as users register (using multer middleware). A lot of the examples show multer is used like this:
router.post('/register', upload ,function (req, res, next) { //upload is the multer middleware
console.log(req.file);
})
How do I add the middleware in my case?

Answer 1

You add the middleware like this:
router.post('/register', upload, handle.register);
Just like the examples you see.
In My Not-So-Humble Opinion
You mention that you have separated your routes from your route handler. In my opinion this is not only misguided but completely wrong.
In the usual MVC architecture you see in other languages, the route and the route handler together makes the controller. In your design you have split your controller into two separate structures. Primarily, this makes your route handling logic and the information of what route it does it for exist in two separate files when they should be located very close to each other.
Now that you are adding middlewares you are finding out that middleawares are installed in routes and with your design it is hard to figure out what middleware is installed for your route handler.
The correct way to separate your business logic from your routes is to follow the MVC design pattern - separate your Model from your Controller (the View is free because it is basically res.json()).
In my not-so-humble opinion you should be creating a model for your user instead of separating controllers into two parts. Your user obviously need a register functionality and the register function should just succeed or fail but should not concern itself with any HTTP error handling because that is the controller's job:
exports.user = {
// .. other methods
register: async function (username, password) {
try {
const user = await db.User.create({username, password});
return user;
} catch (err) {
if(err.code === 11000){
err.message ='Sorry, details already taken';
}
throw err;
}
}
}
Then in your controller (most Express example call "route") you do:
const user = require('./user');
router.post('/register', upload , async (req, res, next) => {
try {
const user = user.register(req.body.username, req.body.password);
const {id, username} = user;
res.status(201).json({id, username});
} catch (err) {
next(err);
}
})
However, this is just my personal opinion.