My mongoose Schema variables are coming back undefined which making the hash not work.

undefined
undefined
Error: data and salt arguments required
    at Object.hash (D:\Folder\Code\Nymadic\nymadic.com\node_modules\bcrypt\bcrypt.js:138:17)
    at model.UserSchema.pre (D:\Folder\Code\Nymadic\nymadic.com\models\user.js:37:12)
    at callMiddlewareFunction (D:\Folder\Code\Nymadic\nymadic.com\node_modules\kareem\index.js:427:23)
    at model.next (D:\Folder\Code\Nymadic\nymadic.com\node_modules\kareem\index.js:58:7)
    at _next (D:\Folder\Code\Nymadic\nymadic.com\node_modules\kareem\index.js:106:10)
    at process.nextTick (D:\Folder\Code\Nymadic\nymadic.com\node_modules\kareem\index.js:452:38)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

const mongoose = require('mongoose');
const bcrypt = require('bcrypt');
const UserSchema = new mongoose.Schema({
    userName: {
        type : String,
        unique : true,
        required : true,
        trim : true
    },
    password: {
        type: String,
        required: true
    },
    firstName: {
        type: String,
        required: true,
        trim: true
    },

    lastName: {
        type: String,
        required: true,
        trim: true
    },
    email: {
        type : String,
        unique : true,
        required : true,
        trim : true
    }
});

// hash password before saving to database
UserSchema.pre('save', (next) => {
    const user = this;
    console.log(UserSchema.userName);
    console.log(UserSchema.password);
    bcrypt.hash(user.password, 10, (err, hash) => {
        if(err) {
            return next(err);
        }
        user.password = hash;
        next();
    })
});


const User = mongoose.model('User', UserSchema);
module.exports = User;

const express = require('express');
const router = express.Router();
const User = require('../models/user.js')


// Home Routes

router.get('/', (req, res, next) => {
    res.render('index');
});

// About Routes

router.get('/about', (req, res, next) => {
    res.render('about', {title : '| About'});
});

// Tools Routes

router.get('/tools', (req, res, next) => {
    res.render('tools', {title : '| Tools'});
});

router.post('/tools', (req, res, next) => {
    var domain = req.body.domain;
    res.end(domain);
});

// Login Routes

router.get('/login', (req, res, next) => {
    res.render('login', {title : '| Login'});
});

router.post('/login', (req, res, next) => {
    res.send(req.body);
    res.end;
});

// Registration Routes 

router.get('/registration', (req, res, next) => {
    res.render('registration', {title : '| Registration'});
});

router.post('/registration', (req, res, next) => {
    res.send(req.body);
    // Check if all fields are filled
    if (req.body.userName && req.body.password && req.body.confirmPassword && req.body.firstName && req.body.lastName && req.body.email) {

        // Confirm Password is the same
        if ( req.body.password != req.body.confirmPassword) {
            const err = new Error ("Passwords don't match!");
            err.status = 400;
            return next(err);
        }

        const userData = {
            userName: req.body.userName,
            password: req.body.password,
            firstName: req.body.firstName,
            lastName: req.body.lastName,
            email: req.body.email
        };

        // Use schema 'create' method to insert document into Mongo
        User.create(userData, (error, user) => {
            if (error) {
                return next(error);
            } else {
                return res.redirect('/profile');
            }
        });
    } else {
        const err = new Error("All Fields Required.");
        err.status = 400;
        return next(err);
    }
});

// Profile Routes

router.get('/profile', (req, res, next) => {
    res.render('profile');
});
module.exports = router;

const express = require('express');
const app = express();
const bodyParser = require('body-parser');
const cookieParser = require('cookie-parser');
const path = require('path');
const mongoose = require('mongoose');

// Mongodb connection
mongoose.connect("mongodb://localhost:27017/nymadic");
const db = mongoose.connection
// Mongo error
db.on('error', console.error.bind(console, 'connection error:'));

// Body Parser and Cookie Parser
app.use(bodyParser.urlencoded({ extended:false }));
app.use(cookieParser());

// Static Files
app.use(express.static(__dirname + '/public'));

// Pug Render Engine
app.set('view engine', 'pug');

// Routes
const mainRoutes = require('./routes');
const wikiRoutes = require('./routes/wiki');

app.use(mainRoutes);
app.use('/wiki', wikiRoutes);

app.listen(8080, () => {
    console.log('Nodejs is running on port 8080...');
  });