NextJS Interview Questions & Answers
Beginner Level Questions
Explore the fundamentals of NextJS with our collection of essential beginner-level questions.
Advance Level Questions
Deepen your NextJS knowledge with our advanced questions that cover state management and cross-platform compatibility.
Expert Level Questions
Master NextJS with our expert-level questions that delve into performance optimization and the inner workings of the NextJS bridge.
Question 1:- What is Next.js and what are its main features?
Answer: - **Next.js** is a React framework that enables server-side rendering (SSR) and static site generation (SSG).
- **Main Features**:
- **Server-Side Rendering (SSR)**: Renders pages on the server.
- **Static Site Generation (SSG)**: Generates static HTML pages at build time.
- **API Routes**: Create API endpoints within the Next.js application.
- **Automatic Code Splitting**: Only loads the necessary JavaScript for each page.
- **File-System Routing**: Pages are created based on the file structure in the pages directory.Question 2:- How does Next.js handle routing?
Answer: - **File-Based Routing**: Next.js uses a file-based routing system.
- **Pages Directory**: Each file in the pages directory automatically becomes a route.
- **Dynamic Routing**: Use square brackets to create dynamic routes, e.g., [id].js.
- **Nested Routes**: Create nested routes by organizing files within subdirectories.Question 3:- What is the difference between getStaticProps and getServerSideProps?
Answer: - **getStaticProps**:
- Runs at build time.
- Used for static site generation (SSG).
- The data fetched is available as static content.
- **getServerSideProps**:
- Runs on every request.
- Used for server-side rendering (SSR).
- The data fetched is fresh on each request.Question 4:- What is Incremental Static Regeneration (ISR) in Next.js?
Answer: - **Incremental Static Regeneration (ISR)** allows you to update static content after the site has been built.
- **How It Works**:
- Use revalidate in getStaticProps to specify a time interval to regenerate the static page.
- On request, Next.js checks if the static page needs to be regenerated.Question 5:- How do you create API routes in Next.js?
Answer: - **API Routes** are created inside the "pages/api" directory.
- **Creating an API Route**:
- Add a file, e.g., pages/api/hello.js.
- Export a function as the default export that handles the request and response.
- **Example**:
```javascript
export default function handler(req, res) {
res.status(200).json({ name: 'John Doe' });
}
```Question 6:- What is the purpose of getStaticPaths in Next.js?
Answer: - **getStaticPaths** is used in conjunction with getStaticProps for dynamic routes.
- **Purpose**:
- It defines which paths will be pre-rendered at build time.
- Returns an object with a paths key containing an array of path objects and a fallback key.
- **Example**:
```javascript
export async function getStaticPaths() {
return {
paths: [{ params: { id: '1' } }, { params: { id: '2' } }],
fallback: false,
};
}
```Question 7:- What are the benefits of using Next.js for SEO?
Answer: - **Next.js** provides several SEO benefits:
- **Server-Side Rendering (SSR)**: Helps search engines crawl and index content easily.
- **Static Site Generation (SSG)**: Generates static HTML for better performance and SEO.
- **Automatic Static Optimization**: Pages that do not require data fetching can be statically optimized.
- **Custom Document**: Customize the HTML document structure to include meta tags for SEO.Question 8:- How do you handle CSS styling in Next.js?
Answer: - **CSS Styling in Next.js** can be handled in several ways:
- **Global CSS**: Import global CSS files in _app.js.
- **CSS Modules**: Use CSS modules for component-level styles. Import CSS files as modules in components.
- **Styled Components**: Use libraries like styled-components for CSS-in-JS styling.
- **Sass**: Support for Sass/SCSS is built-in. Use .module.scss for CSS modules.Question 9:- What is the purpose of the next.config.js file in a Next.js project?
Answer: - **next.config.js** is a configuration file for customizing the behavior of a Next.js application.
- **Common Uses**:
- Configure environment variables.
- Set up custom Webpack configurations.
- Enable experimental features.
- Configure redirects and rewrites.
- **Example**:
```javascript
module.exports = {
env: {
CUSTOM_ENV: process.env.CUSTOM_ENV,
},
};
```Question 10:- How do you use next/image for optimizing images?
Answer: - **next/image** is an Image Optimization component provided by Next.js.
- **Benefits**:
- **Automatic Optimization**: Optimizes images on the fly.
- **Responsive Images**: Automatically serves the appropriate image size for different devices.
- **Lazy Loading**: Images are loaded lazily to improve performance.
- **Example**:
import Image from 'next/image';
export default function MyComponent() {
return <Image src="/example.jpg" alt="Example Image" width={500} height={300} />;
}
```Question 11:- What is the difference between getStaticProps and getServerSideProps in Next.js?
Answer: - **getStaticProps**:
- Runs at build time.
- Used for static site generation (SSG).
- Fetches data and generates static HTML.
- **getServerSideProps**:
- Runs on every request.
- Used for server-side rendering (SSR).
- Fetches data and renders HTML on each request.Question 12:- How do you implement authentication in a Next.js application?
Answer: - **Authentication** in Next.js can be implemented using various methods:
- **Server-Side Authentication**: Handle authentication logic in API routes or server-side rendering methods.
- **Client-Side Authentication**: Use libraries like next-auth for client-side authentication.
- **Session Management**: Store authentication tokens in cookies or local storage.
- **Example**:
```javascript
import { getSession } from 'next-auth/react';
export async function getServerSideProps(context) {
const session = await getSession(context);
if (!session) {
return { redirect: { destination: '/login', permanent: false } };
}
return { props: { session } };
}
```Question 13:- What are API Routes in Next.js and how are they used?
Answer: - **API Routes** are endpoints that allow you to create serverless functions.
- **Usage**:
- Create files in the pages/api directory.
- Export a function that handles HTTP requests.
- **Example**:
```javascript
export default function handler(req, res) {
res.status(200).json({ message: 'Hello World' });
}
```Question 14:- What are Incremental Static Regeneration (ISR) and how do they work in Next.js?
Answer: - **Incremental Static Regeneration (ISR)** allows you to update static content after the site has been built.
- **Usage**:
- Configure revalidate in getStaticProps to specify revalidation intervals.
- The static page will be regenerated in the background and updated on the next request.
- **Example**:
```javascript
export async function getStaticProps() {
return {
props: { /* data */ },
revalidate: 10, // Regenerate at most every 10 seconds
};
}
```Question 15:- How do you handle environment variables in Next.js?
Answer: - **Environment Variables** are managed in Next.js using .env files.
- **Usage**:
- Define variables in .env.local for local development.
- Access variables using process.env.VAR_NAME.
- **Example**:
```javascript
// .env.local
NEXT_PUBLIC_API_URL=https://api.example.com
// In your code
const apiUrl = process.env.NEXT_PUBLIC_API_URL;
```Question 16:- What is the purpose of next/head in a Next.js application?
Answer: - **next/head** is a component for managing the <head> section of your application.
- **Purpose**:
- Add meta tags, titles, and other head elements.
- Customize each page's head content.
- **Example**:
```javascript
import Head from 'next/head';
export default function MyPage() {
return (
<div>
<Head>
<title>My Page Title</title>
<meta name="description" content="My page description" />
</Head>
<p>Page content</p>
</div>
);
}
```Question 17:- How do you implement internationalization (i18n) in Next.js?
Answer: - **Internationalization (i18n)** can be implemented using the next-i18next library or custom solutions.
- **Using next-i18next**:
- Install the library.
- Configure next-i18next.config.js and provide translation files.
- Use hooks to fetch translations.
- **Example**:
```javascript
import { useTranslation } from 'next-i18next';
function MyComponent() {
const { t } = useTranslation('common');
return <p>{t('welcome_message')}</p>;
}
```Question 18:- What are Custom _app and Custom _document in Next.js and how are they used?
Answer: - **Custom _app** (_app.js):
- Used to initialize pages.
- Customize global layout, provide context, or wrap pages with providers.
- **Custom _document** (_document.js):
- Used to customize the HTML document structure.
- Useful for adding global styles or meta tags.
- **Example**:
```javascript
// _app.js
function MyApp({ Component, pageProps }) {
return <Component {...pageProps} />;
}
export default MyApp;
// _document.js
import Document, { Html, Head, Main, NextScript } from 'next/document';
class MyDocument extends Document {
render() {
return (
<Html>
<Head>
<link rel="stylesheet" href="/static/styles.css" />
</Head>
<body>
<Main />
<NextScript />
</body>
</Html>
);
}
}
export default MyDocument;
```Question 19:- How does Next.js handle static and dynamic imports?
Answer: - **Static Imports**:
- Import modules at the top of the file.
- These imports are included in the build and bundled together.
- **Dynamic Imports**:
- Import modules dynamically using import().
- Useful for code-splitting and loading components only when needed.
- **Example**:
```javascript
import dynamic from 'next/dynamic';
const DynamicComponent = dynamic(() => import('./DynamicComponent'));
function MyPage() {
return <DynamicComponent />;
}
```Question 20:- What is the role of next.config.js in Next.js?
Answer: - **next.config.js** is used to customize the behavior and configuration of a Next.js application.
- **Usage**:
- Configure Webpack.
- Set environment variables.
- Enable experimental features.
- Configure redirects and rewrites.
- **Example**:
```javascript
module.exports = {
webpack: (config) => {
// Modify config
return config;
},
env: {
CUSTOM_ENV: process.env.CUSTOM_ENV,
},
};
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