1
What is the MERN stack? Ans.The MERN stack is a collection of JavaScript technologies used to develop full-stack web applications. It consists of MongoDB (database), Express.js (back-end framework), React (front-end library), and Node.js (JavaScript runtime).
2
What is the significance of each component in the MERN stack ? Ans.MongoDB is a NoSQL database for storing data. Express.js is a minimalistic web application framework for Node.js. React is a JavaScript library for building user interfaces, and Node.js is a runtime environment for executing JavaScript code on the server-side.
3
How does React differ from other JavaScript frameworks?Ans.React uses a virtual DOM (Document Object Model) and offers a component-based architecture, which allows for efficient and reusable UI development. It also focuses solely on the view layer, making it easier to integrate with other libraries or frameworks.
4
Explain the concept of a virtual DOM in React.Ans.The virtual DOM is a lightweight copy of the actual DOM. React uses it to improve performance by minimizing direct manipulations of the real DOM. When there are changes in the virtual DOM, React efficiently updates only the necessary parts in the real DOM, resulting in faster rendering.
5
How can you pass data from a parent component to a child component in React?Ans.Data can be passed from a parent component to a child component by using props. Props are like function arguments that can be passed from a parent component to its child components.
Ans.JSX (JavaScript XML) is a syntax extension used in React to write HTML-like code within JavaScript. It allows developers to write components in a more declarative manner, blending JavaScript logic and HTML structure together.
7
Explain the concept of state in React.Ans.State is a JavaScript object that holds the dynamic data of a component. It represents the current state of the component and can be modified over time. When the state changes, React automatically re-renders the component to reflect the updated state.
8
How can you update the state in React?Ans.The state in React can be updated using the setState() method. It merges the new state with the existing state and triggers a re-render of the component.
9
What is the purpose of the componentDidMount() lifecycle method in React ?Ans.The componentDidMount() method is called after the component has been rendered to the DOM. It is commonly used to perform API calls, initialize subscriptions, or set up event listeners.
10
What is Express.js middleware ?Ans.Express.js middleware functions are functions that have access to the request (req) and response (res) objects. They can modify the request or response, invoke the next middleware function, or terminate the request-response cycle.
11
How do you handle routing in Express.js ?Ans.Express.js provides a built-in router middleware that allows you to define routes and their corresponding actions. You can use the app.get(), app.post(), etc., methods to define routes for handling different HTTP methods.
12
What is the purpose of body-parser middleware in Express.js?Ans.The body-parser middleware in Express.js parses the request body and makes it available in req.body. It is commonly used to handle POST requests and retrieve data sent by forms or JSON.
13
What is the purpose of MongoDB in the MERN stack?Ans.MongoDB is a NoSQL document database that stores data in flexible, JSON-like documents. It provides scalability, high performance, and a flexible data model suitable for modern web applications.
14
How do you establish a connection with MongoDB using Node.js? Ans.The mongoose package is commonly used in Node.js to connect to a MongoDB database. You can use the mongoose.connect() method and provide the connection URL along with any necessary options.
15
What is Mongoose in the MERN stack?Ans.Mongoose is an Object Data Modeling (ODM) library for MongoDB and Node.js. It provides a higher-level abstraction for interacting with MongoDB, allowing you to define schemas, perform validations, and perform database operations using JavaScript objects.
16
How do you define a schema in Mongoose? Ans.To define a schema in Mongoose, you can use the mongoose.Schema constructor. You specify the properties and their types within an object, along with any additional options or validators.
17
Explain the concept of middleware in Mongoose.Ans.Middleware in Mongoose allows you to define functions that run before or after specific operations on a model, such as saving or removing a document. It can be used for tasks like data validation, manipulating data, or logging.
18
What is the purpose of React Router in the MERN stack?Ans.React Router is a popular library for handling client-side routing in React applications. It allows you to define different routes and their corresponding components, enabling navigation between different parts of the application without page reloads.
19
How do you handle asynchronous operations in Node.js? Ans.Asynchronous operations in Node.js can be handled using callbacks, Promises, or async/await. Callbacks are traditional but can lead to callback hell. Promises provide a cleaner way to handle async operations, and async/await is a syntactic sugar on top of Promises.
20
What is npm and how is it used in the MERN stack?Ans.NPM (Node Package Manager) is a package manager for JavaScript. It is used to install, manage, and share reusable code packages (libraries, frameworks, etc.) in the MERN stack. It allows developers to easily add and update dependencies in their projects.