NextJS is increasingly becoming a popular react framework that developers can leverage for building server-side rendered applications. Its wide range of offerings makes it an ideal choice for developers in building high-performance web apps.
With such significant importance, NextJS becomes a need-to-know framework for developers. The format of this article is prepared in a way to help you prepare for the NextJs interview questions.
Therefore, this article provides a list of questions and answers that will help you understand various concepts of the NextJS framework and its working. This will help you answer related questions in your NextJS interview.
Beginner
1. What is NextJS? How is it different from React?
NextJS is an open-source framework that developers can use to create server-side rendered React apps. A notable difference between both frameworks is that NextJS has server-side routing and the React framework has client-side routing.
2. What are the advantages of using Next.js over React?
In addition to server-side rendering, NextJS offers the following benefits over React:
Static site generation
Performance optimization
Automatic code splitting
Dynamic imports
Easy deployment
3. How do you create a new Next.js application?
Running the npx create-next-app my-app command in your terminal will help you create a new app with NextJS.
4. Explain Server-side rendering and its importance.
Server-side rendering is a process where a server renders the web page before it is sent to the browser. It helps enhance the SEO as it allows the search engines to index and crawl the web content. Server-side rendering also improves the user experience as well as the page loading time.
5. Explain client-side rendering and its differences from server-side rendering.
When a web page is rendered using JavaScript on a client’s browser after the server sends them the initial JavaScript, CSS, and HTML, it is called client-side rendering. In SSR, the client’s browser will receive a fully-rendered web page whereas in CSR, the server will send an empty page populated with JavaScript.
6. Explain static site generation and its differences from server-side rendering.
When for every web page you create a JavaScript, CSS, and HTML file during the development phase, it is called static site generation. These static files are easy to serve through a CDM whereas HTML in the SSR is generated dynamically and is sent directly to the client’s browser.
7. How do you configure routing in a Next.js application?
A corresponding URL path helps you create new files which allows you to create a new page. This process of routing through files is known as file-based routing.
8. What is the getStaticProps function used for in NextJS?
NextJS utilizes the getStaticProps function during development to fetch the data for static site generation. This data is fetched from a database or an external API. This data is then passed from getStaticProps to a page component as props.
9. How do you pass data between pages in a Next.js application?
Router API, URL query parameters, and some state management libraries such as React Context and Redux are used to pass data between web pages in a NextJS app.
10. How do you deploy a Next.js application?
If you are going with platform-specific deployment then you can use tools like AWS Elastic Beanstalk or CLI from Vercel for app deployment. Another way to deploy the NextJS application is to use the next export command and export all the static files for SSG.
Intermediate
1. What is serverless architecture? How does it relate to NextJS?
In a serverless architecture, the cloud provider would handle all the infrastructure and scale it as per demand. You can deploy the NextJS application on a serverless architecture using serverless platforms such as Google Cloud Functions, and AWS Lambda.
2. Explain the difference between the getStaticProps and getServerSideProps functions of NextJS.
getServerSideProps fetches the data for server-side rendering on the server at runtime and getStaticProps fetches data for static site generation at build time.
3. What is the purpose of the getStaticPaths function in Next.js?
The getStaticPaths function uses dynamic data to create dynamic paths for web pages. It can also generate a list of possible values for dynamic data. Static files are created for every possible value when data returns from getStaticPaths. This function is called enduring a build process.
4. How do you configure dynamic routes in a Next.js application?
In a URL path, the dynamic segments are denoted using square brackets [].
5. What do you need to do for code splitting in NextJS? Explain its importance.
Your code is split automatically into small chunks in NextJS. When a user navigates through the pages, it will load the sections in demand. Code splitting helps reduce the loading time of your pages as well as enhances the performance of your application.
6. What is the purpose of the _app.js file in Next.js?
The app.js file offers context providers, layout components, and global styles to wrap the whole application. Developers use it to add common functionalities to the app. The app.js file is called on each page request.
7. How do you implement authentication in a Next.js application?
There are multiple ways to implement authentication in NextJS such as using OAuth, JWTs, or third-party libraries like NextAuth.js. For server-side authentication, you can use session management and server-side rendering.
8. Explain the difference between the container and the presentational component.
The container component handles the component’s logic and state whereas the presentational component renders the user interface based on the props passed down from the container components.
9. What is React’s useEffect hook used for? Does it have any connection to NextJS?
In a functional component, you can conduct some side effects like updating a document file or fetching data from an API with the help of the useEffect hook. Mainly it is used for fetching data from API or third-party libraries like SWR or Axios.
10. How does the NextJS framework help you manage errors in the app’s codebase?
There are many options to handle errors with NextJS. It includes client-side error handling with React error boundaries, server-side handling with getInitialprops, and custom error pages. For monitoring and reporting errors, you can also leverage third-party libraries like Rollbar and Sentry.
Expert
1. How do you implement internationalization (i18n) in a Next.js application?
The next-i18next library helps you translate and switch languages in your app based on browser settings and user preferences. This library comes in-built with NextJs to support internationalization.
2. What is the getServerSideProps function of NextJS used for? How does its work relate to that of the getInitialProps function?
The getServerSideProps function is useful for fetching data on the server for server-side rendering at runtime. Meanwhile, the getInitialProps function is useful for fetching data on a server or client at runtime.
3. How do you implement server-side caching in a Next.js application?
The Cache-Control header comes pre-built in NextJS to support server-side caching. The getServerSideProps function allows you to set the cache duration for every page. You can also set it in the page component’s cacheControl property.
API responses and database queries are easy to cache using caching libraries such as Memcached and Redis. Developers reduce the load on the server and enhance the static assets’ performance by implementing edge caching or CDM caching.
4. What's the process for NextJS app’s performance optimization?
The performance of the NextJS app can be optimized by implementing various strategies like CDM caching, server-side caching, image optimization, lazy loading, and code splitting. To determine which areas of the app need performance enhancement, you can use performance monitoring tools such as WebPageTest and Lighthouse.
5. How do you implement serverless functions in a Next.js application?
Serverless functions are supported through API Routes features of NextJS. To build a serverless function in NextJS, you first have to apply the server-side logic. Then in the pages/api directory, create a file with a desired endpoint.
6. How do you implement a headless CMS with Next.js?
Utilizing third-party CMS such as Sanity, Strapi, and Contentful, makes the implementation of a headless CMS possible with NextJS. These platforms offer APIs that integrate with the NextJS using functions like getServerSideProps and getStaticProps to fetch and update the content.
7. Nested data structures and complex data models have SSR. How does NextJS help you handle it?
REST APIs and GraphQL would pass the data they fetched from the server to the components as props. For data caching or fetching, you can also use libraries such as React-query and SWR.
8. How do you implement A/B testing in a Next.js application?
Using third-party tools like Optimizely or Google Optimize allows you to track user behavior and create experiments. You can test different variations of your app using their custom features like conditional rendering and feature flags.
9. How do you handle real-time updates in a Next.js application?
Web sockets, server-sent events, and third-party libraries like Socket.io are used to establish real-time connections between the server and the client. So, they are perfect to handle the real-time updates. In the NextJS application, real-time data updates are handled using libraries like redux and react-use.
10. How does NextJS conduct continuous integration and testing?
You can write and run tests for NectJS applications using testing frameworks like Cypress or Jest. Availing continuous integration services like Travis CI and CircleCI would allow you to automate the testing and deployment processes. Moreover, code quality tools such as Prettier and ESLint can help you make sure that your NextJS app’s code is consistent and maintainable.
Conclusion
This post shed some light on the NextJS framework and its practical applications in a Q&A manner. Although we haven’t quite covered the concept of NextJS quite exhaustively, they provide a working knowledge of the framework at all levels.
But many more questions and topics might be asked in the interviews. So it is recommended that you gain practical experience of working with NextJS and be candid about what you know and don't know in the interview.
This post was not written to give you a cheat sheet but to prepare you for the kind of questions that might be asked about NextJS at different levels of experience in an interview. I hope it helps!