Server.js

const express = require('express');
const mongoose = require('mongoose');
const bodyParser = require('body-parser');
const passport = require('passport');
const LocalStrategy = require('passport-local').Strategy;
const port = 3001;
const Book = require('./models/Book.js');
const User = require('./models/User.js');
const session = require('express-session');

const cors = require('cors');
const corsOptions ={
  origin:'http://localhost:3000',
  credentials:true,
  optionSuccessStatus:200
}

passport.use(new LocalStrategy(
    function(username, password, cb) {
      User.findOne({username}, function(err, user) {
        if (err) { return cb(err); }
        if (!user) {
          console.log('Invalid username')
          return cb(null, false);
        }
        if (user.password != password) {
          console.log(user.password);
          console.log(password);
          console.log('Invalid password');
          return cb(null, false);
        }
        return cb(null, user);
      });
    }));


passport.serializeUser(function(user, cb) {
  cb(null, user.username);
});

passport.deserializeUser(function(username, cb) {
  User.findOne({username}, function (err, user) {
    if (err) { return cb(err); }
    console.log(user);
    cb(null, user);
  });
});

const app = express();
app.use(cors(corsOptions));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(session({ secret: 'keyboard cat', resave: false, saveUninitialized: false  }));

app.use(passport.initialize());
app.use(passport.session());

mongoose.connect('mongodb://localhost/book-library', {useNewUrlParser: true, useUnifiedTopology: true});

const db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
  console.log('DB connected');
});

app.post('/api/add-book', (req, res) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Headers', 'origin, content-type, accept');
  const book = new Book({name: req.body.name, author: req.body.author})
  book.save(function (err) {
    if (err) return console.error(err);
    else res.send('Succesfull');
  });
})

app.get('/api/get-books', async (req, res) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Headers', 'origin, content-type, accept');
  await Book.find((err, data) => {
    if(err) res.json(err);
    res.json({items: data});
  });
})

app.post('/api/register-account', (req, res) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Headers', 'origin, content-type, accept');
  const user = new User({username: req.body.username, password: req.body.password})
  user.save(function (err) {
    if (err) return console.error(err);
    else res.send('Succesfull! Account saved!');
  });
})

app.post('/api/login', passport.authenticate('local', {failureRedirect: '/login'}), function (req, res) {
  console.log('Succesfull')
  // console.log(req.user);
  // res.redirect('/')
  res.send('Ok');
})

app.get('/api/me', function (req, res) {
  // console.log(req.user);
  res.json({user: req.user});
})

app.listen(port, () => {
  console.log('Server has been started');
})