How to connect to mongodb via mongoose in nodejs - reactjs

Question

controller/product.controller.js this is the controller class
const Product = require('../models/product.model');
//Simple version, without validation or sanitation
exports.test = function (req, res) {
res.send('Greetings from the Test controller!');
};
exports.product_create = function (req, res) {
const product = new Product(
{
name: req.body.name,
price: req.body.price
}
);
product.save(function (err) {
if (err) {
return next(err);
}
res.send('Product Created successfully')
})
};
models/product.model.js
var mongoose = require('mongoose');
const Schema = mongoose.Schema;
const ProductSchema = new Schema({
name: {type: String, required: true, max: 100},
price: {type: Number, required: true},
});
exports.product_details = function (req, res) {
Product.findById(req.params.id, function (err, product) {
if (err) return next(err);
res.send(product);
})
};
exports.product_delete = function (req, res) {
Product.findByIdAndRemove(req.params.id, function (err) {
if (err) return next(err);
res.send('Deleted successfully!');
})
};
exports.product_update = function (req, res) {
Product.findByIdAndUpdate(req.params.id, {$set: req.body}, function (err, product) {
if (err) return next(err);
res.send('Product udpated.');
});
};
router.put('/:id/update', product_controller.product_update);
// Export the model
module.exports = mongoose.model('Product', ProductSchema);
product.route.js this is used to route
const express = require('express');
const router = express.Router();
// Require the controllers WHICH WE DID NOT CREATE YET!!
const product_controller = require('../controllers/product.controller');
router.post('/create', product_controller.product_create);
// a simple test url to check that all of our files are communicating correctly.
router.get('/test', product_controller.test);
router.put('/:id/update', product_controller.product_update);
router.delete('/:id/delete', product_controller.product_delete);
module.exports = router;
app.js this is the app.js
const express = require('express');
const bodyParser = require('body-parser');
const product = require('./routes/product.route'); // Imports routes for the products
const app = express();
// Set up mongoose connection on mongoAtlas
//https://codeburst.io/writing-a-crud-app-with-node-js-and-mongodb-e0827cbbdafb
const mongoose = require('mongoose');
const dev_db_url = 'mongodb://someuser:abcd1234#ds123619.mlab.com:23619/productstutorial';
const mongoDB = process.env.MONGODB_URI || dev_db_url;
mongoose.connect(mongoDB);
mongoose.Promise = global.Promise;
const db = mongoose.connection;
db.on('error', console.error.bind(console, 'MongoDB connection error:'));
app.use('/products', product);
app.listen(3000,function () {
console.log("Server listen on port: 3000");
});
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));
app.use('/products', product);
So this is the code of the project and please add scripts "start": "node app.js". This will directly be able to use this and update,insert and delete data is also given here with the code.

Answer 1

The setup looks good, However I noticed few points you might missed in app.js. I believe the following slightly modified setup will connect your mongodb properly:
const mongoose = require('mongoose');
const express = require('express');
var cors = require('cors');
const bodyParser = require('body-parser');
const product = require('./routes/product.route'); // Imports routes for the products
const API_PORT = 3000;
const app = express();
app.use(cors());
// Set up mongoose connection on mongoAtlas
//https://codeburst.io/writing-a-crud-app-with-node-js-and-mongodb-e0827cbbdafb
const dev_db_url = 'mongodb://someuser:abcd1234#ds123619.mlab.com:23619/productstutorial';
// connects our back end code with the database
mongoose.connect(process.env.MONGODB_URI || dev_db_url, { useNewUrlParser: true });
let db = mongoose.connection;
db.once('open', () => console.log('connected to the database'));
// checks if connection with the database is successful
db.on('error', console.error.bind(console, 'MongoDB connection error:'));
// bodyParser, parses the request body to be a readable json format
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());
// append /api for our http requests
app.use('/product', product);
// launch our backend into a port
app.listen(API_PORT, () => console.log(`LISTENING ON PORT ${API_PORT}`));

Answer 2

mongoose.connect(url, (err) => {
if (!err) {
app.listen(PORT, () => {
console.log('SERVER WORKING');
})
}
})