10 Surprising Facts About Next-js

Core Features

Next.js is a React framework for building full-stack web applications. It provides developers with a structured approach and various features to build performant and scalable applications. Some of its core features include rendering options like Server-Side Rendering and Static Site Generation, API Routes, File-Based Routing, Code Splitting, Image Optimization, Fast Refresh, TypeScript Support, Built-in CSS Support, and Middleware.

Server-Side Rendering

Server-Side Rendering (SSR) in Next.js means the HTML for a page is generated on the server for each request., This is beneficial for SEO and initial page load performance because the user's browser receives a fully rendered HTML page., This contrasts with traditional Client-Side Rendering (CSR) where the browser receives a minimal HTML file and then uses JavaScript to render the content.,

Static Site Generation

Static Site Generation (SSG) involves pre-rendering pages into HTML at build time., This generated HTML can then be cached and served quickly by a Content Delivery Network (CDN), leading to very fast page load times., SSG is well-suited for pages where the data doesn't change frequently, such as blog posts or marketing pages., Next.js also offers Incremental Static Regeneration (ISR), which allows you to update static pages after the initial build.,

API Routes

Next.js allows you to build API endpoints directly within your application using API Routes., Files placed in the pages/api directory are treated as API endpoints., These are server-side only and don't contribute to the client-side bundle size. API Routes can handle different HTTP methods and support dynamic segments in the URL.,

File-Based Routing

Next.js utilizes a file-based routing system where the file and folder structure in the pages or app directory defines the routes of your application.,, Creating a file in these directories automatically creates a route., This simplifies routing and eliminates the need for manual routing configuration in many cases., Dynamic routes can be created using square brackets in the file name.,

Code Splitting

Next.js automatically performs code splitting, breaking your application's JavaScript into smaller chunks for each route., This means that when a user visits a page, only the necessary code for that page is loaded, improving initial page load times., You can further optimize this with dynamic imports to load components only when they are needed.,,

Image Optimization

Next.js includes a built-in Image Optimization API and component that automatically optimizes images. This can include resizing, compressing, and serving images in modern formats like WebP, which significantly improves performance and loading times.,

Fast Refresh

Fast Refresh is a Next.js feature that provides instantaneous feedback on code changes during development.,, It allows you to see updates in the browser almost immediately without a full page reload, and in many cases, it preserves the component's state.,

TypeScript Support

Next.js has integrated support for TypeScript, providing features like automatic installation of necessary packages and configuration.,, It also includes a custom TypeScript plugin for enhanced type-checking and autocompletion in code editors., Using TypeScript can improve code quality, maintainability, and developer productivity.,

Built-in CSS Support

Next.js supports various ways of handling CSS, including CSS Modules, Global Styles, and external stylesheets., CSS Modules provide local scoping for your styles, preventing naming collisions.,, Global styles can be imported to apply styles across the entire application.,

Middleware

Middleware in Next.js allows you to run code before a request is completed.,, This enables you to intercept and modify incoming requests or responses, perform authentication checks, handle redirects, or modify headers.,,, Middleware runs before routes are matched.

Server-Side Rendering

Server-Side Rendering (SSR) is a technique where the content of a web page is generated on the server before being sent to the client's browser. This is different from traditional client-side rendering (CSR), where the browser receives a minimal HTML file and then uses JavaScript to fetch data and build the page in the browser.

Next.js provides built-in support for SSR, allowing developers to easily implement this rendering strategy. When a request comes in for a page configured for SSR in Next.js, the server fetches the necessary data and renders the full HTML for that page. This fully rendered HTML is then sent to the browser.

One of the primary benefits of SSR is improved Search Engine Optimization (SEO). Search engine crawlers can easily read the content of a fully rendered page, as opposed to waiting for JavaScript to execute in CSR. Additionally, SSR can lead to faster perceived performance for users, especially on slower networks or devices, because the initial HTML load already contains the visible content.

Next.js makes implementing SSR straightforward, often by simply exporting an async function like getServerSideProps from a page component. This function runs on the server for every request and the data it returns is passed as props to the page component for rendering.

Static Site Generation

Static Site Generation (SSG) is a method where HTML pages are generated at build time. With Next.js, you can pre-render pages using SSG, which means the HTML for the page is created when you build your application.

This approach offers significant advantages. Since the pages are already built and served as static files, they can be delivered very quickly by a Content Delivery Network (CDN). This leads to improved performance and a better user experience.

SSG is particularly beneficial for content that doesn't change frequently, such as blog posts, documentation pages, or product listings. Because the content is pre-rendered, it's also highly optimized for search engines (SEO).

Next.js makes implementing SSG straightforward. You can use specific data fetching functions like getStaticProps to fetch data at build time and pass it to your page components. This pre-renders the page with the data already included.

While ideal for static content, Next.js also offers ways to combine SSG with client-side rendering or even incrementally update static pages after the initial build, providing flexibility for various use cases.

API Routes

Next.js provides a simple way to build APIs directly within your application using API Routes. These routes reside in the pages/api directory (or app/api in newer versions) and function as serverless functions.

Instead of needing a separate backend project, you can create API endpoints that handle various HTTP methods like GET, POST, PUT, and DELETE. This allows you to build full-stack applications where your frontend and API live in the same Next.js project.

Each file in the pages/api or app/api directory becomes an API endpoint. For example, creating a file named pages/api/users.js would automatically create an API endpoint accessible at /api/users. This file-based routing simplifies API development and organization.

API Routes are a powerful feature for fetching data, handling form submissions, or connecting to databases directly from your Next.js application's backend.

File-Based Routing

Next.js simplifies navigation in your web application through a feature called file-based routing. Instead of manually configuring routes, you create files and folders within a designated directory, and Next.js automatically maps these structures to URL paths. This approach makes organizing your project and understanding your application's routes intuitive and straightforward.

In the App Router (the recommended approach for new Next.js applications), this designated directory is typically the app directory at the root of your project. For example, creating a file named app/about/page.js will automatically create a route accessible at /about. Similarly, a file at app/products/page.js maps to the /products route.

Nested folders create nested routes. A file at app/dashboard/settings/page.js will be available at /dashboard/settings.

Next.js also supports dynamic routes, allowing you to create routes that match variable segments in the URL. This is done by using square brackets in the folder or file name. For instance, app/products/[productId]/page.js creates a route that matches paths like /products/1 or /products/abc. The value within the brackets (productId in this case) is then available as a parameter to your page component, allowing you to fetch or display data specific to that segment.

This convention-over-configuration approach significantly speeds up development by eliminating the need for a separate routing configuration file and keeping your file structure closely aligned with your URL structure.

Code Splitting

Code splitting is a technique used in web development to break down a large JavaScript bundle into smaller, more manageable chunks. This is important because loading a single, massive JavaScript file can significantly slow down the initial loading time of a webpage.

Next.js automatically handles code splitting for you based on its file-based routing system. Each page defined in the pages or app directory becomes its own independent JavaScript bundle. When a user navigates to a specific page, only the code necessary for that page is downloaded and executed.

Beyond automatic page-based splitting, Next.js also supports dynamic imports. This allows developers to manually split code within a page or component, loading parts of the application only when they are needed, such as when a button is clicked or a certain element becomes visible.

The primary benefit of code splitting is improved application performance. By reducing the amount of JavaScript that needs to be downloaded and parsed initially, pages load faster, leading to a better user experience, especially on devices with slower network connections.

Image Optimization

Next.js offers a built-in solution for image optimization through its next/image component. This component extends the standard HTML <img> element, providing automatic features to enhance performance. Images are a significant part of web content and can impact page load times and metrics like Largest Contentful Paint (LCP).

The next/image component automatically optimizes images in several ways:

• Size Optimization: It serves images in the correct size for each device and utilizes modern formats like WebP and AVIF, which offer better compression and quality compared to older formats like JPEG.
• Visual Stability: The component helps prevent Cumulative Layout Shift (CLS) by automatically determining the appropriate dimensions for images, especially for statically imported ones. For remote images, you need to manually define width and height to prevent layout shifts.
• Faster Page Loads: Images are lazy loaded by default, meaning they only load when they enter the user's viewport. This improves initial page load performance.
• Asset Flexibility: It supports on-demand image resizing, even for images hosted on remote servers.

Using the next/image component simplifies image management and optimization, especially for websites with many images. It handles responsive images automatically, creating multiple copies at different sizes and serving the most suitable one based on the user's screen size.

For local images, Next.js automatically determines the width and height, which helps prevent CLS. When using remote images, you need to configure a list of allowed hostnames in your next.config.js file.

The component also supports features like automatic image compression, placeholder images (including a blur effect), and control over image quality.

Fast Refresh

Fast Refresh is a key feature in Next.js that significantly enhances the developer experience. It's a React capability integrated into Next.js that allows you to see changes you make to your code reflected in the browser almost instantly, without losing the temporary state of your components. This means you can edit your React components, styles, rendering logic, and event handlers, and the updates will appear within a second in most cases.

This feature replaced the older React Hot Loader and offers a more robust and reliable Hot Module Replacement (HMR). Fast Refresh is designed to preserve component state across updates, which is a major advantage during development. For instance, if you have a counter component and click a button several times, then make a change to the component's code, the counter's state will be preserved after the Fast Refresh.

Fast Refresh is enabled by default in Next.js applications from version 9.4 onwards, requiring no extra configuration.

How It Works

When you edit a file that exports only React component(s), Fast Refresh updates only the code for that specific file and re-renders the component. If you modify a file containing exports that are not React components but are imported by React components, Fast Refresh will re-run that file and any files that import it. However, if you edit a file that's imported by parts of your application outside of the React tree, Fast Refresh will fall back to performing a full page reload.

State Preservation

Fast Refresh generally preserves the local state of function components and Hooks. This includes state managed with useState and references created with useRef, as long as their arguments or the order of Hook calls don't change. Hooks with dependencies, such as useEffect, useMemo, and useCallback, will always update during a Fast Refresh.

There are situations where local state might be reset. This can happen with class components (state is not preserved for them), or if the edited file has exports in addition to a React component. To force a state reset and component remount, you can add // @refresh reset anywhere in the file you are editing.

Error Handling

Fast Refresh is also designed with error resilience in mind. If you introduce a syntax error during development, you can fix it and save the file, and the error will disappear automatically without needing a manual reload. Fast Refresh will continue to work once syntax or runtime errors are resolved.

TypeScript Support

Next.js offers excellent built-in support for TypeScript, a strongly typed superset of JavaScript. This allows developers to leverage type safety, improving code quality and developer productivity. Integrating TypeScript into a Next.js project is straightforward, providing a smoother development experience, especially for larger applications.

Built-in CSS Support

Next.js offers robust built-in support for styling your applications, providing several methods to manage your CSS. This flexibility allows developers to choose the approach that best suits their project's needs and their personal preferences.

CSS Modules

One of the primary ways to handle CSS in Next.js is through CSS Modules. This feature is built-in and doesn't require any extra configuration. CSS Modules locally scope your CSS classes by automatically generating unique class names during the build process. This prevents naming collisions and makes it easier to manage component-specific styles, ensuring that styles applied to one component don't unintentionally affect other parts of your application. To use CSS Modules, you simply create a CSS file with the .module.css extension and import it into your component.

Global CSS

While CSS Modules are excellent for component-level styling, you might need to apply styles globally across your application. Next.js supports global CSS, which is typically imported in the root layout file (app/layout.tsx in the App Router or pages/_app.js in the Pages Router). This is suitable for defining styles that affect the entire application, such as typography or a CSS reset. However, it's recommended to use global styles sparingly and rely on CSS Modules for most styling to avoid potential conflicts and maintainability issues in larger applications.

Other Styling Methods

Beyond CSS Modules and Global CSS, Next.js is also compatible with other popular styling solutions. You can integrate Tailwind CSS, a utility-first framework, Sass, a powerful CSS preprocessor, or CSS-in-JS libraries like styled-components or Emotion. This broad support ensures that you can leverage your preferred styling tools within a Next.js project.

Next.js's built-in CSS support, particularly with CSS Modules and straightforward global styling, simplifies the styling process and promotes a more organized and maintainable codebase. The framework also includes features like Fast Refresh for local development, providing an instant feedback loop as you make style changes. In production builds, CSS files are automatically minified and code-split for optimized loading.

Middleware

Middleware in Next.js allows you to run code before a request is completed. It acts as a bridge between the incoming request and the server response, enabling you to intercept requests and execute logic based on the request properties.

This functionality runs at the edge, which means it executes before the cached content is served. This is beneficial for performance as it doesn't block the rendering of your pages.

You can use Middleware for various purposes, such as:

• Authenticating users and protecting routes.
• Redirecting users based on location or other criteria.
• Rewriting URLs.
• Adding headers to responses.
• Implementing A/B testing or feature flags.

Middleware provides a powerful way to add custom logic that applies to requests across your Next.js application without modifying individual pages or API routes.