MongoDB connection with mongodb driver in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the MongoClient in the mongodb driver?

The MongoClient is used to connect to a MongoDB database server. It manages the connection and allows you to perform database operations.

beginner

Which method is used to establish a connection to MongoDB using the mongodb driver?

The connect() method of MongoClient is used to establish a connection to the MongoDB server.

beginner

What does the connection string URI typically include?

The connection string URI includes the protocol (mongodb:// or mongodb+srv://), the server address, port (optional), and database name. It may also include username and password for authentication.

intermediate

Why should you close the MongoDB connection after operations?

Closing the connection frees up resources and avoids potential memory leaks or too many open connections to the database server.

beginner

Show a simple example of connecting to MongoDB using the mongodb driver in Node.js.

import { MongoClient } from 'mongodb';

const uri = 'mongodb://localhost:27017';
const client = new MongoClient(uri);

async function run() {
  try {
    await client.connect();
    console.log('Connected to MongoDB');
  } finally {
    await client.close();
  }
}

run().catch(console.dir);

Which class do you use to connect to MongoDB in the official Node.js driver?

A MongoClient

B MongoConnection

C MongoDB

D MongoServer

The MongoClient class is the official way to connect to MongoDB using the Node.js driver.

What method do you call to start a connection to MongoDB?

A start()

B init()

C connect()

D open()

The connect() method on MongoClient establishes the connection.

What is the correct prefix for a MongoDB connection string URI?

A http://

B sql://

C ftp://

D mongodb://

MongoDB connection strings start with mongodb:// or mongodb+srv://.

Why is it important to close the MongoDB connection after use?

A To save battery on the server

B To free resources and avoid too many open connections

C To speed up queries

D To encrypt data

Closing the connection frees resources and prevents too many open connections.

Which of these is a valid way to import MongoClient in Node.js with ES modules?

A import { MongoClient } from 'mongodb';

B const MongoClient = require('mongodb');

C import MongoClient from 'mongodb';

D const { MongoClient } = require('mongodb');

With ES modules, use import { MongoClient } from 'mongodb';.

Explain how to connect to a MongoDB database using the mongodb driver in Node.js.

Think about the steps from importing to closing the connection.

What are the key parts of a MongoDB connection string URI?

Consider what you need to tell the driver to find and access your database.

Practice

1. What is the main purpose of using MongoClient from the mongodb package in Node.js?

easy

A. To start a web server

B. To create a new database schema

C. To connect to a MongoDB database server

D. To run SQL queries on MongoDB

Solution

1. Step 1: Understand MongoClient's role

   MongoClient is a class used to establish a connection to a MongoDB server from Node.js.

2. Step 2: Identify the correct purpose

   It does not create schemas or run SQL queries; it only manages connections to MongoDB.

3. Final Answer:

   To connect to a MongoDB database server -> Option C

4. Quick Check:

   MongoClient connects to MongoDB [OK]

Hint: MongoClient is for connecting to MongoDB servers [OK]

Common Mistakes:

• Confusing MongoClient with schema creation tools
• Thinking MongoClient runs SQL queries
• Assuming MongoClient starts web servers

2. Which of the following is the correct way to import MongoClient from the mongodb package in Node.js?

easy

A. const { MongoClient } = require('mongodb');

B. import MongoClient from 'mongodb';

C. const MongoClient = require('mongodb');

D. import { MongoClient } from 'mongodb';

Solution

1. Step 1: Identify Node.js import syntax

   In Node.js with CommonJS, destructuring import uses const { MongoClient } = require('mongodb');.

2. Step 2: Check other options

   const MongoClient = require('mongodb'); imports the entire module object, not the MongoClient class; import MongoClient from 'mongodb'; is ES module default import (incorrect here); import { MongoClient } from 'mongodb'; is ES module named import (valid only in ES modules).

3. Final Answer:

   const { MongoClient } = require('mongodb'); -> Option A

4. Quick Check:

   Destructured require syntax = const { MongoClient } = require('mongodb'); [OK]

Hint: Use destructuring with require for MongoClient in Node.js [OK]

Common Mistakes:

• Using default import syntax in CommonJS
• Requiring the module without accessing .MongoClient
• Mixing ES module and CommonJS syntax

3. What will be the output of the following code snippet if the MongoDB URI is correct and the connection is successful?

const { MongoClient } = require('mongodb');
async function run() {
  const client = new MongoClient('mongodb://localhost:27017');
  await client.connect();
  console.log('Connected successfully to server');
  await client.close();
}
run();

medium

A. Error: MongoClient is not defined

B. No output

C. SyntaxError: await is only valid in async function

D. Connected successfully to server

Solution

1. Step 1: Analyze the async function and connection

   The function run is async, creates a MongoClient, connects, logs success, then closes.

2. Step 2: Check for errors or output

   Since URI is correct and await is used properly inside async function, it logs the success message.

3. Final Answer:

   Connected successfully to server -> Option D

4. Quick Check:

   Successful connect logs message [OK]

Hint: Async function with await logs success message [OK]

Common Mistakes:

• Using await outside async function
• Not calling client.connect() before logging
• Forgetting to close the client

4. Identify the error in the following code snippet that tries to connect to MongoDB:

const { MongoClient } = require('mongodb');
const client = new MongoClient('mongodb://localhost:27017');
client.connect();
console.log('Connected');
client.close();

medium

A. Incorrect MongoDB URI format

B. Missing async/await for connect and close methods

C. MongoClient is not imported correctly

D. console.log syntax error

Solution

1. Step 1: Check usage of connect and close

   Both connect() and close() return promises and must be awaited or handled asynchronously.

2. Step 2: Identify missing async/await

   The code calls these methods without await or then, so connection may not complete before logging or closing.

3. Final Answer:

   Missing async/await for connect and close methods -> Option B

4. Quick Check:

   Async methods need await [OK]

Hint: Always await connect() and close() in async functions [OK]

Common Mistakes:

• Calling async methods without await
• Assuming connect() is synchronous
• Not wrapping calls in async function

5. You want to connect to a MongoDB server using the mongodb driver in Node.js and perform a simple query to find all documents in the users collection. Which of the following code snippets correctly connects, queries, and closes the connection?

hard

A. const { MongoClient } = require('mongodb');
async function run() {
const client = new MongoClient('mongodb://localhost:27017');
await client.connect();
const db = client.db('testdb');
const users = await db.collection('users').find().toArray();
console.log(users);
await client.close();
}
run();

B. const { MongoClient } = require('mongodb');
const client = new MongoClient('mongodb://localhost:27017');
const db = client.db('testdb');
const users = db.collection('users').find();
console.log(users);
client.close();

C. import { MongoClient } from 'mongodb';
const client = new MongoClient('mongodb://localhost:27017');
await client.connect();
const users = client.db('testdb').collection('users').find().toArray();
console.log(users);
await client.close();

D. const MongoClient = require('mongodb');
const client = new MongoClient('mongodb://localhost:27017');
client.connect();
const users = client.db('testdb').collection('users').find().toArray();
console.log(users);
client.close();

Solution

1. Step 1: Check for proper async/await usage

   const { MongoClient } = require('mongodb'); async function run() { const client = new MongoClient('mongodb://localhost:27017'); await client.connect(); const db = client.db('testdb'); const users = await db.collection('users').find().toArray(); console.log(users); await client.close(); } run(); uses async function with await for connect, query, and close, ensuring proper sequence.

2. Step 2: Validate correct import and method calls

   const { MongoClient } = require('mongodb'); async function run() { const client = new MongoClient('mongodb://localhost:27017'); await client.connect(); const db = client.db('testdb'); const users = await db.collection('users').find().toArray(); console.log(users); await client.close(); } run(); correctly imports MongoClient, connects, queries with toArray(), logs, and closes connection.

3. Final Answer:

   Uses destructured import, async function, await connect(), find().toArray(), await close() -> Option A

4. Quick Check:

   Async connect, query, close with await = const { MongoClient } = require('mongodb'); async function run() { const client = new MongoClient('mongodb://localhost:27017'); await client.connect(); const db = client.db('testdb'); const users = await db.collection('users').find().toArray(); console.log(users); await client.close(); } run(); [OK]

Hint: Use async/await for connect, query, and close in sequence [OK]

Common Mistakes:

• Not awaiting connect or query results
• Using incorrect import syntax
• Calling methods without async context