Why my middleware is not checking if the email already exists? - node.js

Question

I am authenticating people using passportJS. The problem I have recently realised is the fact that users are able to register for more than one account. I have created a middleware to check whether the email is already in use but somehow it is still passing the test.
var User = require('../models/users');
var authMethods = {};
authMethods.isInUse = function(req,res,next){
User.findOne({"email" : req.body.email}, (err,user) => {
if(user){
req.flash('error',"This mail is already in use.");
res.redirect('/register');
}else {
return next();
}
});
}
module.exports = authMethods;
In my authentication page I am calling the middleware inside the route to meet the condition.
router.post('/register',authMethods.isInUse ,multipart(),function(req, res) {
var image = fs.readFileSync(req.files.image.path);
var profilePic = {data : image, contentType : 'image/png'};
var user = new User({
username: req.body.username,
email: req.body.email,
password: req.body.password,
occupation: req.body.occupation,
phone: req.body.phone,
profilePic : profilePic,
firstName : req.body.firstName,
lastName : req.body.lastName
});
user.save(function(err) {
req.logIn(user, function(err) {
req.flash("success", "Welcome to the site " + user.username);
res.redirect('/flats');
});
});
});
I haven't been able to spot the faulty approach that's causing the problem.

Answer 1

If multipart() does what I think it does (parse the request data into req.body), then req.body will probably not be populated in your middleware because it's being called before the multipart middleware.
Try switching the middleware functions around:
router.post('/register', multipart(), authMethods.isInUse, function(req, res) {
...
});