MongoDB is a NoSQL database that stores data in flexible, JSON-like documents.
Explain BSON.
BSON (Binary JSON) is a binary-encoded serialization of JSON-like documents used in MongoDB.
What is a Collection in MongoDB?
A collection is a group of MongoDB documents. It’s equivalent to an RDBMS table.
Differentiate between MongoDB and SQL databases.
MongoDB is a NoSQL database, while SQL databases are relational databases. MongoDB uses a flexible, schema-less document model.
How does MongoDB ensure high availability?
MongoDB achieves high availability through replica sets, which are copies of the same data distributed across multiple servers.
Explain the difference between MongoDB and MySQL.
MongoDB is a NoSQL, document-based database, while MySQL is a relational database. MongoDB is schema-less, providing more flexibility in data representation.
What is indexing in MongoDB, and why is it important?
Indexing is the process of creating an index to improve the speed of data retrieval operations. It is important for quickly locating and accessing specific documents in a collection.
How does MongoDB handle transactions?
MongoDB supports multi-document transactions, allowing operations on multiple documents to be grouped together and executed atomically.
What is sharding in MongoDB?
Sharding is a method used to distribute data across multiple servers to improve horizontal scalability. It involves breaking up a large collection into smaller, more manageable chunks.
Explain the Map-Reduce function in MongoDB.
Map-Reduce is a data processing paradigm used in MongoDB for batch processing and aggregation of data. It consists of two steps: mapping and reducing.
What is Express.js?
Express.js is a web application framework for Node.js. It simplifies the process of building robust web applications and APIs.
Explain middleware in Express.js.
Middleware are functions that have access to the request and response objects. They can modify these objects or terminate the request-response cycle.
What is routing in Express.js?
Routing in Express.js refers to determining how an application responds to a client request to a particular endpoint.
How to handle errors in Express.js?
You can handle errors using middleware functions with four parameters (err, req, res, next).
What is the purpose of the body-parser middleware in Express.js?
body-parser is used to parse the incoming request bodies in a middleware before your handlers, available under the req.body property.
Differentiate between app.get() and app.use() in Express.js.
app.get() is used for handling HTTP GET requests, while app.use() is a generic middleware function that can be used to handle any type of HTTP request.
What is the purpose of the Express.js Router?
The Express.js Router allows you to modularize your routes and middleware, making your code more organized and maintainable.
Explain the role of the Express.js request object.
The request object (req) in Express.js contains information about the HTTP request, including parameters, headers, and the body of the request.
How does Express.js handle sessions?
Express.js can use middleware like express-session to handle sessions. Sessions are often stored in-memory or in a database, and a session ID is sent to the client as a cookie.
What is the purpose of the next() function in Express.js middleware?
next() is a function that passes control to the next middleware function in the stack. It is used to move to the next piece of middleware in the request-response cycle.
Explain React.js.
React.js is a JavaScript library for building user interfaces, particularly for single-page applications where you want a fast, interactive user experience.
What are state and props in React?
State is an object that represents the parts of the app that can change, while props are immutable data passed from parent to child components.
What is JSX in React?
JSX is a syntax extension for JavaScript recommended by React. It allows mixing HTML with JavaScript code.
What is the significance of virtual DOM in React?
The virtual DOM is a lightweight copy of the real DOM. React uses it to improve performance by updating only the parts of the DOM that need it.
Explain React lifecycle methods.
React components have lifecycle methods that allow you to run code at particular points in a component’s life.
What are React hooks?
React hooks are functions that enable functional components to use state and lifecycle features that were previously only available in class components.
Explain the concept of prop drilling in React.
Prop drilling occurs when props are passed down multiple levels of nested components. It can be mitigated using React Context or state management libraries like Redux.
What is React Context, and when might you use it?
React Context provides a way to pass data through the component tree without having to pass props manually at every level. It’s useful for sharing state between components.
How does React handle forms?
React handles forms using controlled components, where form elements are controlled by state. It allows for more dynamic manipulation of form data.
What is React’s reconciliation process?
React’s reconciliation process is the algorithm it uses to diff and update the virtual DOM efficiently. It helps in determining the minimal number of DOM manipulations needed.
What is Node.js?
Node.js is a JavaScript runtime built on Chrome’s V8 JavaScript engine. It allows you to execute JavaScript code on the server side.
What is npm?
npm (Node Package Manager) is the package manager for JavaScript. It is used for managing and sharing packages of code.
Explain the event-driven programming in Node.js.
Node.js is built on an event-driven architecture, using an event loop to handle asynchronous operations.
What is the purpose of the package.json file?
package.json is a metadata file in a Node.js project. It contains project-specific configuration and dependencies.
How does Node.js handle child threads?
Node.js is single-threaded, but it can handle concurrency by using the event loop and delegating tasks to the operating system’s kernel.
Explain the concept of callback hell and how to avoid it in Node.js.
Callback hell (or “pyramid of doom”) occurs when multiple nested callbacks are used. It can be avoided using promises, async/await, or modularizing code.
What is the purpose of the process object in Node.js?
The process object in Node.js provides information about, and control over, the current Node.js process. It can be used for accessing environment variables, exiting the process, etc.
How does Node.js handle asynchronous operations?
Node.js uses an event-driven, non-blocking I/O model to handle asynchronous operations. It employs callbacks, promises, and async/await for managing asynchronous code.
What is the role of the Node Package Manager (npm) in a Node.js project?
npm is used for managing dependencies, running scripts, and sharing code packages in Node.js projects. It simplifies the process of installing and updating packages.
Explain the concept of middleware in Node.js.
Middleware in Node.js is a function that has access to the request, response, and the next middleware function in the application’s request-response cycle. It can modify the request or response or terminate the cycle.
Explain the concept of Single Page Applications (SPAs).
SPAs load a single HTML page and dynamically update the content as the user interacts with the app, typically using AJAX to fetch data.
What is the role of Babel in a MERN stack application?
Babel is used to transpile ECMAScript 6+ code into backward-compatible JavaScript that can run in older browsers.
How does MERN stack handle Cross-Origin Resource Sharing (CORS)?
CORS is handled by configuring the server (Express.js) to include appropriate headers allowing or denying cross-origin requests.
What is Redux, and why might you use it in a MERN stack application?
Redux is a state management library for JavaScript applications. It’s often used in React applications to manage the state in a predictable way.
Explain the role of Webpack in a MERN stack.
Webpack is a module bundler used to bundle JavaScript files for usage in a browser. It can also transform, bundle, or package just about any resource or asset.
How can you secure your Node.js application?
Secure your Node.js application by validating and sanitizing user input, using HTTPS, employing authentication and authorization, and keeping dependencies updated.
What is JWT, and how is it used in a MERN stack application?
JWT (JSON Web Token) is a compact, URL-safe means of representing claims to be transferred between two parties. It’s often used for authentication in MERN applications.
How does React Router work for client-side routing in a MERN stack application?
React Router enables navigation among views in a React Application, allowing the user to experience a single-page web application.
Explain the concept of server-side rendering (SSR) in React.
SSR is the process of rendering React components on the server side instead of the client side. It improves performance and SEO.
What are the advantages of using MERN stack for web development?
Advantages include a unified language (JavaScript) for the entire stack, ease of scalability, a large and active developer community, and the ability to build modern, dynamic web applications.
How do you optimize the performance of a MERN stack application?
Performance optimization techniques include minimizing HTTP requests, using a Content Delivery Network (CDN), lazy loading, and optimizing database queries.
What is the purpose of the create-react-app tool?
create-react-app is a command-line tool that sets up a new React project with a sensible default configuration, making it easier to start building React applications.
Explain the concept of HOCs (Higher-Order Components) in React.
HOCs are functions that take a component and return a new component with additional props or behavior. They are used for code reuse, logic abstraction, and component composition.
How does server-side rendering (SSR) impact SEO in a MERN stack application?
SSR improves SEO by delivering fully rendered HTML to search engine crawlers, making content more accessible and improving search engine rankings.
What is the purpose of the async and await keywords in JavaScript, and how are they used in a MERN stack application?
async and await are used for handling asynchronous code in a synchronous manner, making it more readable and easier to reason about. They are commonly used in conjunction with promises in MERN applications.
How can you deploy a MERN stack application?
MERN stack applications can be deployed to various platforms, such as Heroku, AWS, or Azure. Deployment involves configuring the server, setting up a database, and optimizing the application for production.
Explain the concept of WebSocket and its role in a MERN stack application.
WebSockets provide full-duplex communication channels over a single, long-lived connection. They are used in MERN applications for real-time communication between the client and server.
What is the role of the webpack-dev-server in a MERN stack development environment?
webpack-dev-server is a development server that provides live reloading, allowing developers to see changes in real-time without manually refreshing the browser during development.
How does error handling differ between client-side and server-side in a MERN stack application?
Client-side errors are generally handled in the browser, often using tools like React’s ErrorBoundary. Server-side errors are handled on the server, and appropriate responses or error pages are sent to the client.
Explain the concept of CORS and how to handle it in Express.js.
CORS (Cross-Origin Resource Sharing) is a security feature implemented by browsers. In Express.js