Top 20 MERN Stack Interview Questions and Answers

MERN Stack Interview Questions and Answers

MongoDB, Express.JS, React.JS, and Node.js (MERN) are the four JavaScript-based technologies that comprise the open-source MERN stack. Gaining expertise in the MERN stack will enable you to leverage a variety of domains to create dynamic websites and web applications.

MERN Stack Interview Questions and Answers for Freshers

1. What is MERN Stack?

MERN stands for Node.js, React.js, Express.js, and MongoDB. It’s a full-stack JavaScript framework designed to help create contemporary websites.

2. Explain MongoDB, Express.js., React.js, and Node.js.

MongoDB: A NoSQL database called MongoDB uses flexible documents that resemble JSON to store data.

Express.js: It is a Node.js web application framework that offers a feature-rich feature set for developing mobile and web applications. 

React.js: Facebook developed the JavaScript library React.js to create user interfaces. It makes building reusable user interface components possible.

Node.js: A runtime environment called Node.js allows JavaScript code to be executed server-side, facilitating the creation of scalable and fast online applications.

3. What benefits does the MERN stack offer?

The benefits of MERN are JavaScript development, efficiency, scalability, flexibility, etc.

4. Describe JSX’s function in React.Js.

UI creation is made easier with the help of JSX, a JavaScript syntactic extension that enables HTML and JavaScript to be combined in React components.

5. How is routing handled in MERN?

React.js uses packages like React Router to handle client-side routing, whereas Express.js handles server-side routing.

6. In Express.js, what does a middleware mean?

Functions with access to and the ability to change the request and response objects are known as middleware. They are employed in error handling, authentication, and logging.

7. How is a MERN application deployed?

Applications built using MERN can be launched on many platforms, including DigitalOcean, AWS, and Heroku. Usually, you would create the Express backend and connect it to a MongoDB database while building the React front end. 

8. Describe the React.js virtual DOM idea.

A thin replica of the real DOM is the virtual DOM. By updating only the components that have changed instead of re-rendering the full DOM, React.js uses it to increase performance.

9. Describe props in React.

React components take props, which are short for properties, as inputs. They are immutable within the child component and permit data transmission from parent to child components.

10. Describe RESTful APIs and the way Express.js makes them easier to create.

RESTful APIs adhere to the Representational State Transfer (REST) principles. Express.js supports middleware and provides HTTP utility methods, making it easy to build RESTful APIs, manage requests, and design routes.

MERN Stack Interview Questions and Answers for Experienced

11. Which performance optimization strategies have you applied to MERN applications?

Some examples of performance optimization techniques are as follows:

• Code splitting and lazy loading in React.js.
• Reducing bundle size with Webpack and other tools.
• Streamlining database queries and indexes in MongoDB.
• Achieving server-side caching with Redis or Memcached.
• Utilizing CDN (Content Delivery Network) to serve static assets.

12. How would a MERN stack application be deployed?

The necessary steps to deploying a MERN stack application are as follows:

Step 1: Set up a server environment (such as Heroku, AWS, or DigitalOcean)

Step 2: Create the React.js front end

Step 3: Configure an Express.js server to deliver the produced files

Step 4: Establish a connection to a MongoDB database 

Using continuous integration/continuous deployment (CI/CD) pipelines for automated deployment operations and version control systems like Git are common deployment procedures.

13. In a MERN application, how are exceptions and errors handled?

Try-catch blocks, Express.js’s error-handling middleware, and global error handlers—which centralize error-handling logic—can all be used to handle errors and exceptions. 

Debugging and monitoring can also be facilitated by reporting problems to a centralized system like Splunk or Loggly.

14. In a MERN application, how are authorization and authentication handled?

Libraries like Passport.js for Express.js and JWT (JSON Web Tokens) can be used to implement authentication. Role-based access control (RBAC) middleware is commonly used to handle authorization, where users’ roles determine their access privileges to specific resources.

15. What benefits and drawbacks come with using Redux in a MERN application?

Redux is a centralized state management solution that simplifies the management of intricate application states and promotes data transfer among components. But, particularly in smaller apps, it can add complexity and boilerplate code.

16. What techniques are used to protect a MERN application from typical security risks?

Some examples of security tactics are:

• Using secure authentication techniques like JWT.
• Implementing HTTPS
• Input validation and sanitization 
• Guarding against cross-site scripting (XSS)
• Cross-site request forgery (CSRF)
• Regularly upgrading dependencies to fix known vulnerabilities.

17. Describe the microservices architecture and its role in MERN stack app development.

Applications are divided into smaller, independently deployable services using a microservices architecture. 

Each service in the MERN stack may be developed with Node.js and Express.js, utilizing message queues or HTTP for communication, and a common MongoDB database for data sharing.

18. Explain the mongoose.

To define objects using a strongly typed schema that can be mapped to a MongoDB document, utilize the object document mapper, also known as Mongoose. 

Consequently, Mongoose offers a schema-based approach to application data modeling. 

Mongoose was enhanced with typecasting, validation, query building, business logic hooks, and many other features. 

19. Define data modeling

Data modeling is used in Mongoose and MongoDB. 

• Creating a data model for the current data before putting it in a database is known as data modeling. 
• The data object, its relationship, and the rules governing the data’s connectivity are all represented in the data model.
• Data modeling enforces business rules, compliance, and policy while enabling data visualization.
• Conventions, values, semantics, security, and data quality are all guaranteed to be consistent through data modeling.

20. Define REPL in NodeJS.

A program called the Read Eval Print Loop (REPL) takes commands, evaluates them, and prints the results. Therefore, REPL creates an environment for entering commands and systems that respond to the output in the same manner as Unix or Linux did.

Conclusion

Utilize this resource that contains MERN stack interview questions and answers to review your skills on MongoDB, Express.Js, React.js, and Node.js. Prepare well for the interviews with international-recognized certification through our MERN stack training in Chennai.