Next.js Framework: Building React Applications with Server-Side Rendering

This guide explores Next.js, a popular React framework for building high-performance web applications. Learn about its features, including server-side rendering (SSR) and static site generation (SSG), and discover why it's a preferred choice for creating SEO-friendly and scalable React applications.

Next.js Interview Questions and Answers

What is Next.js?

Question 1: What is Next.js?

Next.js is a popular React framework for building web applications. It simplifies building server-side rendered (SSR) and statically-generated (SSG) React applications. Next.js handles many of the complexities of React development, such as routing, code splitting, and server-side rendering, making it easier to create high-performance web applications. It provides a streamlined development experience and includes built-in support for features like SEO, API routes, and image optimization.

Why Use Next.js?

Question 2: Why Use Next.js?

Next.js is preferred because it:

  • Simplifies setting up React applications (no webpack configuration needed).
  • Handles code splitting and optimization for improved performance.
  • Provides automatic server-side rendering for SEO and faster initial loads.
  • Supports both static site generation and server-side rendering.
  • Simplifies routing (file-system based).
  • Is highly extensible (customizable server, routing, and plugins).
  • Supports API routes for building serverless functions.

Installing Next.js

Question 3: Installing Next.js

Steps:

  1. Ensure Node.js is installed.
  2. Create a project directory.
  3. Create a Next.js app using create-next-app (recommended): npx create-next-app my-app or yarn create next-app my-app
  4. (Alternatively) Manually install using npm or yarn: npm install next react react-dom or yarn add next react react-dom. Then add scripts to your `package.json` file.
  5. Run the development server: npm run dev or yarn dev.

The default port is 3000 (http://localhost:3000).

Learn more about installing Next.js

Prominent Features of Next.js

Question 4: Prominent Features of Next.js

Next.js key features:

  • Server-side rendering (SSR).
  • Static site generation (SSG).
  • Automatic code splitting.
  • File-system based routing.
  • API routes.
  • Hot Module Replacement (HMR).
  • Image optimization.

Types of Websites Using Next.js

Question 5: Types of Websites Using Next.js

Next.js is well-suited for:

  • Static websites.
  • Server-rendered applications.
  • SEO-friendly websites.
  • Progressive web apps (PWAs).

Next.js and Redux

Question 6: Using Next.js with Redux

Yes, Next.js and Redux can be used together. Redux helps manage application state in complex Next.js applications.

Data Fetching in Next.js

Question 7: Data Fetching in Next.js

Next.js recommends using `getInitialProps` (for pages) or `getServerSideProps` to fetch data. These asynchronous functions retrieve data before rendering the page on the server-side or client-side.

Example: getInitialProps

export async function getInitialProps({query}) {
    const res = await fetch(`http://example.com/api/products?category=${query.category}`)
    const data = await res.json()
    return {
        props: {
            products: data
        }
    }
}

Setting up CDN in Next.js

Question 8: Setting up CDN in Next.js

To use a CDN (Content Delivery Network) with Next.js, configure the `assetPrefix` option in your `next.config.js` file. If your CDN is on a different domain, add the `crossOrigin` option to enable cross-origin requests.

next.config.js

const isProd = process.env.NODE_ENV === 'production';
module.exports = {
  assetPrefix: isProd ? 'https://cdn.mydomain.com/' : '',
  crossOrigin: 'anonymous'
};

Create React App vs. Next.js

Question 9: Create React App vs. Next.js

Create React App is a tool for setting up a basic React project; Next.js is a full-featured React framework with built-in features for server-side rendering, routing, and other advanced functionalities. Next.js is generally preferred for larger, more complex projects that need these features.

Next.js Development Scripts

Question 10: Next.js Development Scripts

Typical scripts in `package.json`:

package.json scripts

"scripts": {
  "dev": "next dev",
  "build": "next build",
  "start": "next start",
  "lint": "next lint"
}
  • `dev`: Starts the development server.
  • `build`: Creates a production build.
  • `start`: Starts the production server.
  • `lint`: Runs the linter.

Pages and Routing

Question 10: Pages and Routing in Next.js

Next.js uses a file-system based routing system. Each JavaScript file in the `pages` directory is a page. The filename determines the route. For example, `pages/about.js` maps to `/about`.

Disabling ETag Generation

Question 11: Disabling ETag Generation in Next.js

To disable ETag generation (used for caching) for static assets in a Next.js application, you need to configure the Express.js static middleware.

next.config.js

const path = require('path');
const express = require('express');

module.exports = {
  webpack: (config, { buildId, dev, isServer, defaultLoaders, webpack }) => {
    config.plugins.push(new webpack.DefinePlugin({
        'process.env.BUILD_ID': JSON.stringify(buildId)
    }));
    return config;
  },
  async rewrites() {
    return [
      {
        source: '/api/:path*',
        destination: `https://api.example.com/:path*`,
      }
    ];
  },
  async redirects() {
    return [
      {
        source: '/old-blog/:path*',
        destination: '/new-blog/:path*',
        permanent: true,
      }
    ];
  },
  generateBuildId: async () => {
    // For example, get the latest git commit hash here.
    return 'my-build-id';
  },
  exportPathMap: async function(defaultPathMap) {
    return {
      '/': { page: '/' },
      '/about': { page: '/about' }
    }
  },
  exportTrailingSlash: true,
  future: {
    webpack5: true,
  },
  images: {
    domains: ['example.com'],
  },
  poweredByHeader: false,
  compress: true,
  useFileSystemPublicRoutes: true,
  assetPrefix: process.env.NODE_ENV === 'production' ? 'https://cdn.mydomain.com/' : '',
  crossOrigin: 'anonymous'
};

Configuring Build ID

Question 12: Configuring Build ID in Next.js

The `generateBuildId` function in Next.js' `next.config.js` lets you customize the build ID. This helps in cache invalidation between builds.

next.config.js

module.exports = {
  generateBuildId: async () => {
    return 'my-custom-build-id'; 
  }
};

Creating a Page Directory

Question 13: Creating a Page Directory

You create a page in Next.js by creating a file inside the `pages` directory. The filename determines the route.

Example: pages/index.js

function HomePage() {
    return <div>Welcome to Next.js!</div>;
}
export default HomePage;
Output (at http://localhost:3000)

Displays "Welcome to Next.js!"

Custom Error Pages

Question 14: Creating Custom Error Pages

Create a custom error page by creating a file named `_error.js` within the `pages` directory.

Example: _error.js

import React from 'react';

const Error = ({ statusCode }) => {
  return (
    <p>
      {statusCode
        ? `An error ${statusCode} occurred on server`
        : 'An error occurred'}
    </p>
  );
};

Error.getInitialProps = ({ res, err }) => {
  const statusCode = res ? res.statusCode : err ? err.statusCode : 404;
  return { statusCode };
};

export default Error;

Code Splitting

Question 15: Code Splitting in Next.js

Code splitting breaks down your application's JavaScript code into smaller bundles. This improves load times by loading only the necessary code for a given page or route.

Enabling AMP

Question 16: Enabling AMP in Next.js

You can support AMP (Accelerated Mobile Pages) using Next.js with either an AMP-first or hybrid approach.

Hosting Next.js with Nginx

Question 17: Hosting Next.js with Nginx

Next.js requires a Node.js server for handling requests. While you can use Nginx or other web servers for static assets, a Node.js server is generally used to handle routing and server-side rendering. It is not a simple static site generator.