Mongo db connection not establishing - mongodb

Question

Below is the code which i used to up the server. It is running in the localhost server 3000.
app.use('/', books);
app.listen(3000, function(){
console.log('Server running at port 3000: http://localhost:3000')
});
Below code throws mongodb error. Dont know what exactly the error. Below is my code
var express = require('express');
var router = express.Router();
var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://127.0.0.1:27017';
// SHOW LIST OF BOOKS
router.get('/book', function(req, res, next) {
MongoClient.connect(url, function(error, db) {
if (error) throw error;
var dbo = db.db("BookStore");
dbo.collection("Books").find().toArray(function(err, result) {
if (err) throw err;
res.send(result);
console.log(result);
db.close();
});
});
});
// SHOW BOOK with ISBN
router.get('/book/:isbn', function(req, res, next) {
var isbn = parseInt(req.params.isbn);
MongoClient.connect(url, function(error, db) {
if (error) throw error;
var dbo = db.db("BookStore");
var query = { "isbn": isbn };
dbo.collection("Books").findOne(query, function(err, result) {
if (err) throw err;
res.send(result);
console.log(result);
db.close();
});
});
});
// Add BOOK
router.post('/book', function(req, res, next) {
MongoClient.connect(url, function(error, db) {
if (error) throw error;
var dbo = db.db("BookStore");
var myobj = {
"isbn":req.body.isbn,
"publisher":req.body.publisher,
"title":req.body.title,
"authors":req.body.authors,
"publishedDate":req.body.publishedDate,
"price":req.body.price
};
dbo.collection("Books").insertOne(myobj, function(err, result) {
if (err) throw err;
res.send('Book with '+req.body.isbn+' is successfully added');
db.close();
});
});
});
// UPDATE BOOK
router.put('/book/:isbn', function(req, res, next) {
var isbn = parseInt(req.params.isbn);
MongoClient.connect(url, function(error, db) {
if (error) throw error;
var dbo = db.db("BookStore");
var query = { "isbn": isbn };
var newvalues = { $set: {
"publisher":req.body.publisher,
"title":req.body.title,
"authors":req.body.authors,
"publishedDate":req.body.publishedDate,
"price":req.body.price
}
};
dbo.collection("Books").updateOne(query, newvalues, function(err, result) {
if (err) throw err;
res.send('Book with '+req.params.isbn+' is successfully updated');
db.close();
});
});
});
// DELETE BOOK
router.delete('/book/:isbn', function(req, res, next) {
var isbn = parseInt(req.params.isbn);
MongoClient.connect(url, function(error, db) {
if (error) throw error;
var dbo = db.db("BookStore");
var query = { "isbn": isbn };
dbo.collection("Books").deleteMany(query, function(err, result) {
if (err) throw err;
res.send('Book with '+req.params.isbn+' is successfully removed');
db.close();
});
});
});
module.exports = router;
Code Explanation:
We are creating a route to our application called 'Books.' So
whenever anybody browses to http://localhost:3000/books of our application, the code snippet defined for this route will be
executed.
Here we are getting all of the records in our 'Books'
collection through the db.collection('Books').find() command. We are then assigning this collection to a variable called cursor. Using this cursor variable, we will be able to browse through all of the records of the collection.

Answer 1

Run sudo mongod in the terminal

Answer 2

Is it impossible to connect even if you change the value assigned to the variable url to mongodb://[user_name]:[password]#127.0.0.1:27017/[your_database_name]?authSource=admin ?

Answer 3

Actually, the error is related to MongoDB version(MongoClient.connect(url, function(error, db)), MongoDB developers have changed their API. I don't know which version, it throws an error when you use MongoClient.connect(url, function(error, db).
So it should be MongoClient.connect(url, function(err, client)
Link to api-doc
And do not forget to run mongod