Crack Your Next.js Interview

• Server-Side Rendering (SSR): Next.js allows rendering React components on the server before sending them to the client, improving performance and SEO.
• Static Site Generation (SSG): It pre-renders pages at build time, useful for blogs or e-commerce sites.
• API Routes: You can build a backend using API routes in the same codebase without needing an external server.
• File-Based Routing: Next.js automatically creates routes based on the file structure inside the pages directory.
• Client-Side Rendering (CSR): Like React, Next.js also supports traditional client-side rendering.
• Image Optimization: Built-in image optimization capabilities that reduce image sizes and enhance loading times.
• Automatic Code Splitting: Next.js splits the code into smaller bundles, which are loaded only when required, improving performance.
• TypeScript Support: Native support for TypeScript, enabling strict typing and better developer experience.
• Incremental Static Regeneration (ISR): Pages can be statically generated at runtime and updated incrementally.
• Fast Refresh: Provides an instant feedback loop while coding, similar to React's hot reloading.

Next.js is a React-based framework that adds powerful features like server-side rendering, static site generation, file-based routing, and more, enabling developers to build highly optimized web applications. On the other hand, React.js is a JavaScript library for building user interfaces, primarily focused on client-side rendering. Let's explore the key differences between Next.js and React.js in the table below:

Next.js provides built-in image optimization through the <Image> component, designed to improve performance and loading times by automatically optimizing images based on the user’s device and screen size. This feature allows images to load quickly without sacrificing quality, enhancing both user experience and SEO.

How Next.js Image Optimization Works:

1. Automatic Resizing:
   • The <Image> component detects the screen size of the device and serves appropriately sized images. This reduces the amount of data downloaded, especially on smaller screens.
2. Responsive and Layout Options:
   • With properties like fill, responsive, and intrinsic, you can specify how an image should behave across various screen sizes. The component handles responsive images seamlessly, making it easier to build layouts that adapt to different devices.
3. Automatic Format Conversion:
   • Next.js serves images in modern formats, such as WebP, when supported by the browser. WebP files are typically smaller and load faster than traditional JPEG or PNG formats, reducing page load time.
4. Lazy Loading:
   • Images are lazy-loaded by default, meaning they only load when they appear in the viewport. This reduces the initial page load time, especially for pages with many images.
5. Caching:
   • Next.js caches optimized images to avoid re-optimizing on each request, reducing server load and improving speed. Cached images are stored either locally on the server or in a CDN (Content Delivery Network) if configured.
6. Support for External Images:
   • Next.js allows you to load images from external domains by configuring the domains option in next.config.js. This is useful for loading images from a CDN or other external sources.

Key Properties of the <Image> Component:

• src: The source of the image, which can be either a local path or an external URL.
• width and height: Define the size of the image and are required for static images to help Next.js optimize layout shifts.
• layout: Controls how the image behaves. Options include:
  • fill: Allows the image to scale to fill its container.
  • responsive: Provides a responsive image that scales based on the viewport width.
  • intrinsic: Resizes to the intrinsic dimensions of the image but is responsive within the bounds of those dimensions.
• priority: Allows you to prioritize loading of key images, useful for hero images or above-the-fold content.

Example Usage:

import Image from 'next/image';
 
export default function Profile() {
  return (
    <Image
      src="/profile.jpg"
      width={200}
      height={200}
      alt="Profile Picture"
      priority // This image loads with high priority
    />
  );
}
 

Configuring Image Optimization in next.config.js:

In next.config.js, you can customize image optimization settings. For example:

// next.config.js
module.exports = {
  images: {
    domains: ['example.com'], // Allow images from external domains
    deviceSizes: [640, 768, 1024, 1280, 1600], // Customize breakpoints for responsive images
    imageSizes: [16, 32, 48, 64, 96], // Define sizes for icons or smaller images
  },
};
 

Advantages of Next.js Image Optimization:

• Reduced Page Load Time: By serving smaller, optimized images, page load times are reduced significantly.
• Improved SEO and Core Web Vitals: Faster image load times improve Core Web Vitals metrics like LCP (Largest Contentful Paint), impacting SEO.
• Automatic Lazy Loading: Only images in the viewport are loaded initially, which speeds up page load time.

Next.js image optimization is a powerful feature that handles complex tasks behind the scenes, improving performance with minimal developer effort.