MERN Stack

Question 1

What is MongoDB?

Answer 1

MongoDB is a NoSQL database that stores data in a flexible, JSON-like format called BSON.

Question 2

What are the key features of MongoDB?

Answer 2

Key features include scalability, flexible schema, high performance, indexing, replication, and support for sharding.

Question 3

What is a document in MongoDB?

Answer 3

A document is a single record in MongoDB, stored as a BSON object similar to a JSON object.

Question 4

What is a collection in MongoDB?

Answer 4

A collection is a group of MongoDB documents, analogous to a table in relational databases but with a dynamic schema.

Question 5

What is the difference between MongoDB and a relational database?

Answer 5

MongoDB is a NoSQL database with a flexible schema and document-based storage, while relational databases use fixed schemas and tables with rows and columns.

Question 6

What is an index in MongoDB?

Answer 6

An index in MongoDB is a special structure that improves the speed of data retrieval operations on a collection.

Question 7

What is replication in MongoDB?

Answer 7

Replication is the process of synchronizing data across multiple servers to ensure high availability and redundancy.

Question 8

What is recording in MongoDB?

Answer 8

Recording seems to be a typo; it likely refers to ‘sharding’ or ‘replication.’ Assuming replication: it syncs data across servers for reliability.

Question 9

How does the aggregation framework work in MongoDB?

Answer 9

The aggregation framework processes data through a pipeline of stages (e.g., filter, group, sort) to transform and analyze data.

Question 10

How do you perform a backup and restore in MongoDB?

Answer 10

Use mongodump to create a backup and mongorestore to restore data from the backup.

Question 11

What is Express.js?

Answer 11

Express.js is a minimal and flexible Node.js web application framework that simplifies building APIs and web servers.

Question 12

What are the main features of Express.js?

Answer 12

Main features include middleware support, routing, HTTP utility methods, and easy integration with templating engines.

Question 13

How do you create a simple server using Express.js?

Answer 13

Use require(‘express’), create an app with express(), and start it with app.listen(port), e.g., app.get(‘/’, (req, res) => res.send(‘Hello’)).

Question 14

What is middleware in Express.js?

Answer 14

Middleware are functions that have access to the request and response objects, used for tasks like logging, authentication, or parsing.

Question 15

How do you define routes in Express.js?

Answer 15

Define routes using app.get(), app.post(), etc., with a path and callback, e.g., app.get(‘/users’, (req, res) => res.send(‘Users’)).

Question 16

How do you handle errors in Express.js?

Answer 16

Use a middleware with four parameters (err, req, res, next) to catch and handle errors, e.g., app.use((err, req, res, next) => res.status(500).send(err)).

Question 17

What is the role of the next function in middleware?

Answer 17

The next function passes control to the next middleware function in the stack, allowing sequential processing.

Question 18

How do you handle form data and file uploads in Express.js?

Answer 18

Use middleware like body-parser for form data and multer for file uploads, configuring them to parse req.body or req.files.

Question 19

How can you manage different environments in an Express.js application?

Answer 19

Use environment variables with process.env, and switch configurations (e.g., dev, prod) using a config file or package like dotenv.

Question 20

What are some common security best practices when using Express.js?

Answer 20

Use Helmet for headers, sanitize inputs, enable CORS appropriately, use HTTPS, and validate/escape data to prevent attacks.

Question 21

What is React.js?

Answer 21

React.js is a JavaScript library for building user interfaces, especially single-page applications, using a component-based architecture.

Question 22

What are the main features of React.js?

Answer 22

Main features include virtual DOM, component reusability, JSX, hooks, and efficient updates via a diffing algorithm.

Question 23

What is JSX?

Answer 23

JSX is a syntax extension for JavaScript that allows writing HTML-like code within React components, which is transpiled to JavaScript.

Question 24

What are components in React.js?

Answer 24

Components are reusable building blocks in React that encapsulate UI and logic, either as functional or class-based entities.

Question 25

What is the difference between functional and class components?

Answer 25

Functional components are simpler, hook-based functions, while class components use ES6 classes with lifecycle methods.

Question 26

What is state in React.js and how is it used?

Answer 26

State is an object that holds data specific to a component, managed with useState in functional components or this.setState in class components.

Question 27

What are props in React.js and how do they differ from state?

Answer 27

Props are immutable data passed to components from parents, while state is mutable data managed within the component.

Question 28

What is the virtual DOM and how does React use it?

Answer 28

The virtual DOM is a lightweight copy of the real DOM. React uses it to compute differences and update the real DOM efficiently.

Question 29

What are React hooks and name a few commonly used hooks?

Answer 29

Hooks are functions to use state and lifecycle features in functional components. Common hooks: useState, useEffect, useContext.

Question 30

How do you manage side effects in React.js?

Answer 30

Use the useEffect hook to handle side effects like data fetching, subscriptions, or DOM manipulations after render.

Question 31

What is Node.js?

Answer 31

Node.js is a runtime that allows executing JavaScript on the server side, built on Chrome's V8 engine.

Question 32

What are the main features of Node.js?

Answer 32

Main features include non-blocking I/O, event-driven architecture, single-threaded model, and a rich ecosystem via npm.

Question 33

How does Node.js handle asynchronous operations?

Answer 33

Node.js uses an event loop, callbacks, promises, and async/await to handle asynchronous operations non-blockingly.

Question 34

What is the event loop in Node.js?

Answer 34

The event loop is a mechanism that allows Node.js to perform non-blocking I/O operations by offloading tasks to the system kernel.

Question 35

What are streams in Node.js and how are they used?

Answer 35

Streams are objects for handling data in chunks, used for reading/writing files, network communications, and processing large datasets efficiently.

Question 36

What is the difference between process.nextTick() and setImmediate()?

Answer 36

process.nextTick() runs before I/O events in the next iteration, while setImmediate() runs after I/O events in the next iteration.

Question 37

How do you handle errors in Node.js?

Answer 37

Use try-catch for synchronous code, handle errors in callbacks/promises, or use a global error handler with process.on('uncaughtException').

Question 38

What are some common use cases for Node.js?

Answer 38

Common use cases include real-time apps (chat), APIs, microservices, streaming, and server-side rendering.

Question 39

What are modules in Node.js and how do you use them?

Answer 39

Modules are reusable code units. Use require() to import (CommonJS) or import/export (ES6) with a package.json configuration.

Question 40

How do you manage package dependencies in a Node.js project?

Answer 40

Manage dependencies with a package.json file, using npm install to add packages and npm update to keep them current.