Implement multiple middleware for authentication and Multer in NodeJS - node.js

Question

I have a form sent from an Angular front-end to a nodeJS server.
This form can contain input file (not mandatory) and other text fields.
So i'm using FormData for the multipart encoding.
Here is the code from my Angular service :
const formDataGenerated = generateFormDataFromForm(form);
formDataGenerated.append('id', this.tokenStorage.getUser().id);
if (file !== null) {
formDataGenerated.append('file', file);
formDataGenerated.set('riddleFile', file.name);
}
return this.http.post(QUEST_API + 'create', formDataGenerated)
.pipe(
map((res: any) => {
return res;
})
);
i'm using this route in nodeJS: router.post('/create', [auth, multer], questCtrl.create);
The second middleware 'multer' is working fine
const util = require("util");
const multer = require("multer");
const path = require('path')
const pathFile = path.resolve('./resources/assets/uploads/')
let storage = multer.diskStorage({
destination: (req, file, cb) => {
cb(null, pathFile);
},
filename: (req, file, cb) => {
cb(null, file.originalname);
},
});
let uploadFile = multer({
storage: storage,
}).single("file");
let uploadFileMiddleware = util.promisify(uploadFile);
module.exports = uploadFileMiddleware;
And when i'm in my questController i can get all the form values like this :
const formValue = JSON.parse(JSON.stringify(req.body));
At this point, my file is correctly uploaded and i can get all the needed data from the submited form
But now, i want to add another middleware that will allow me to authenticate the user using JwtToken.
In this code i need to access req.body.id that is submitted in FormData
But now, due to the multipart enconding i can't access this property so easily.
So my question is, how to implement my 'auth' middleware and after the user is authorized, continue on my multer middleware and controller (as it's currently working)

Answer 1

Generally, the request in Express falls through middleware until it is not broken by res.send(). The "jump" to next middleware is secured with next() function, that is passed to the middleware as third argument.
app.use((req, res, next) => {
if (req.body.password === 'mypassword') {
req.myAuthentication = true // append whatever props to req
console.log('I have authenticated the user!')
next() <-- sends request to the next middleware
})
app.get('/authenticated', (req, res, next) => {
if (req.myAuthentication) { // use your property in next middleware
res.sendFile('authenticated.html')
}
res.status(401)
next() <-- no effect, res.send/res.status finishes the middleware fn