Why database connectivity matters in Node.js - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why is database connectivity important in Node.js applications?

Choose the best reason why connecting to a database is crucial for most Node.js apps.

A It automatically fixes bugs in the app without developer input.

B It speeds up the app by running all code inside the database server.

C It allows the app to store and retrieve data dynamically, making it interactive and useful.

D It replaces the need for any server-side code in the app.

💡 Hint

Think about what apps do with user information or content they show.

Database connectivity lets apps save and get data like user info or posts. Without it, apps can't remember or change data.

❓ component_behavior

intermediate

What happens if a Node.js app fails to connect to its database?

Consider a Node.js app that tries to fetch user data but the database connection fails. What will likely happen?

A The app will crash or show an error because it can't get the needed data.

B The app will continue normally and show cached data automatically.

C The app will switch to a backup database without any code changes.

D The app will run faster because it skips database calls.

💡 Hint

Think about what happens when the app asks for data but none arrives.

If the app can't connect to the database, it can't get data and usually throws an error or stops working properly.

📝 Syntax

advanced

Identify the correct way to connect to a MongoDB database using Node.js and the official driver.

Which code snippet correctly connects to a MongoDB database using the mongodb package?

Node.js

const { MongoClient } = require('mongodb');
const uri = 'mongodb://localhost:27017';

async function connect() {
  // connection code here
}

A

const client = MongoClient(uri);
client.connect();
console.log('Connected');

B

const client = new MongoClient(uri);
await client.connect();
console.log('Connected');

C

const client = new MongoClient();
await client.connect(uri);
console.log('Connected');

D

const client = new MongoClient(uri);
client.connect(() => console.log('Connected'));

💡 Hint

Remember to create a new MongoClient with the URI and use await to connect.

Option B correctly creates a new MongoClient with the URI and uses await client.connect() to establish the connection.

❓ state_output

advanced

What will be logged after this Node.js database connection code runs?

Consider this code snippet using pg package for PostgreSQL:

const { Client } = require('pg');
const client = new Client({ connectionString: 'postgresql://user:pass@localhost/db' });

async function run() {
  await client.connect();
  const res = await client.query('SELECT 1 AS number');
  console.log(res.rows[0].number);
  await client.end();
}

run();

What will be printed to the console?

A null

B undefined

C Error: connection refused

D 1

💡 Hint

The query selects a constant number 1 as 'number'.

The query returns one row with a column 'number' equal to 1, so res.rows[0].number is 1.

🔧 Debug

expert

Why does this Node.js code throw a 'TypeError: client.query is not a function'?

Examine the code below:

const { Client } = require('pg');
const client = Client({ connectionString: 'postgresql://user:pass@localhost/db' });

async function run() {
  await client.connect();
  const res = await client.query('SELECT NOW()');
  console.log(res.rows[0]);
  await client.end();
}

run();

Why does it throw the error?

A Because <code>Client</code> was called without <code>new</code>, so <code>client</code> is undefined and has no <code>query</code> method.

B Because the connection string is invalid and causes <code>query</code> to fail.

C Because <code>await</code> cannot be used outside an async function.

D Because <code>client.end()</code> is missing a callback function.

💡 Hint

Check how the Client object is created.

The Client constructor must be called with new. Without it, client is not an instance and lacks query.