book.js

const router = require('express').Router();
let Book = require('../model/book.model');

router.route('/').get((req, res) => {
  Book.find()
    .then(books => res.json(books))
    .catch(err => res.status(400).json('Error: ' + err));
});

router.route('/add').post((req, res) => {
  const book_id = req.body.book_id;
  const book_name = req.body.book_name;
  const author = req.body.author;
  const price = Number(req.body.price);

  const newBook = new Book({_id: book_id,book_name,author,price});

  newBook.save()
    .then(() => res.json('Book added!'))
    .catch(err => res.status(400).json('Error: ' + err));
});

router.route('/:id').get((req, res) => {
  Book.findById(req.params.id)
    .then(books => res.json(books))
    .catch(err => res.status(400).json('Error: ' + err));
});

router.route('/:id').delete((req, res) => {
  Book.findByIdAndDelete(req.params.id)
    .then(() => res.json('Book deleted.'))
    .catch(err => res.status(400).json('Error: ' + err));
});

router.route('/update/:id').post((req, res) => {
  Book.findById(req.params.id)
    .then(book => {
      book.book_id = req.body.book_id;
      book.book_name = req.body.book_name;
      book.author = req.body.author;
      book.price = Number(req.body.price);

      book.save()
        .then(() => res.json('Book updated!'))
        .catch(err => res.status(400).json('Error: ' + err));
    })
    .catch(err => res.status(400).json('Error: ' + err));
});

module.exports = router;