Nextjs Dynamic Routes And Url Parameters Complete Guide

Top 10 Questions and Answers on Next.js Dynamic Routes and URL Parameters

Dynamic routes in Next.js allow you to create pages with routes that depend on external data. Instead of a static path like /about, a dynamic route might be something like /posts/[id]. These routes are defined by creating pages inside the pages directory using square brackets around a file or folder name ([param].js). When a request is made to such a route, Next.js provides the parameter data as a prop (params) to the component.

2. How do I create a dynamic route in Next.js?

To create a dynamic route in Next.js, simply add a page to your application within the pages folder and enclose the filename or folder name in square brackets to signify it as a dynamic parameter. For example, if you want to create a dynamic route for blog posts where each post can be identified by an ID, create a file at location pages/posts/[id].js. This file will automatically become dynamic and can handle requests like /posts/1, /posts/2, etc.

3. Can I use multiple parameters in a dynamic route?

Yes, you can definitely use multiple parameters in a dynamic route in Next.js. To include more than one parameter, nest additional folders or files within the dynamic route structure. Here's an example: pages/shop/[section]/[category]/[productID].js. If you visit /shop/electronics/mobiles/45678, Next.js will provide the parameters (section, category, productID) in the params object.

4. How can I pass URL parameters to a dynamic route in Next.js?

With Next.js, URL parameters are typically defined within the route itself using square brackets to specify which parts of the URL should be captured as parameters. However, if you're generating dynamic paths during server-side rendering (SSR) or static site generation (SSG), you'll need to provide them in the getStaticPaths or getServerSideProps functions. In your component, these parameters will be available through the router object or as props.

5. How do I access URL parameters in a dynamic Next.js page using the useRouter hook?

You can access URL parameters in any Next.js dynamic route by importing the useRouter hook from next/router. Once imported, you can call the hook in a functional component to get access to the router object, which contains a query property. Inside this property lies your URL parameters. For example, in pages/posts/[id].js, you can extract the id like so:

import { useRouter } from 'next/router'

const Post = () => {
  const router = useRouter()
  const { id } = router.query

  return (
    <div>
      <h1>Post ID: {id}</h1>
    </div>
  )
}

export default Post

6. Is there a difference between dynamic routes and query parameters?

Absolutely. Dynamic routes in Next.js refer to routes that have some part of their path dynamically set, e.g., /users/[userid]. These paths map directly to specific files in the pages folder. On the other hand, query parameters are optional key-value pairs appended to a URL after a question mark (e.g., /search?tag=news). They do not alter the pathname; instead, they provide additional information that can be accessed via the request object or via the router.query object.

7. How do I handle fallback in dynamic routes with getStaticPaths?

In Next.js, when you use getStaticPaths for SSG, you must define all possible paths at build time. When a user navigates to a path that hasn't been pre-rendered, they will initially see a fallback view (which could be either a loading page or a complete page rendered on the server side). After rendering, subsequent visits to the same path will display the pre-rendered page. To enable fallback rendering, return an object from getStaticPaths with the fallback key set to true:

export async function getStaticPaths() {
  // Call an external API endpoint to get posts
  const res = await fetch('https://api.example.com/posts')
  const posts = await res.json()

  // Get the paths we want to pre-render based on posts
  const paths = posts.map((post) => ({
    params: { id: post.id },
  }))

  // We'll pre-render only these paths at build time.
  // { fallback: true } means other routes should 404.
  return { paths, fallback: true }
}

8. How can I redirect from a dynamic route in Next.js?

In Next.js, the redirect option in a getServerSideProps function is used to redirect the user to another page. Since dynamic routes involve server-side rendering functions, using redirects within these functions is straightforward. Here’s an example of how you might redirect based on a parameter:

export async function getServerSideProps(context) {
  const { slug } = context.params;
  
  // Perform redirection logic here
  if(slug === 'old-post'){
    return {
      redirect: {
        destination: '/new-location',
        permanent: true,
      }
    };
  }

  return { props: {} };
}

9. Are dynamic routes compatible with both SSR and SSG?

Absolutely! Next.js allows you to use dynamic routes with server-side rendering using getServerSideProps and with static site generation using getStaticPaths and getStaticProps. This flexibility means you can optimize performance for both server-rendered and statically-generated pages depending on your application requirements.

10. How do dynamic routes work in development mode versus production mode?

*During development, dynamic routing in Next.js works seamlessly due to its development server capabilities, allowing it to render the correct component whenever a request matches a dynamic path pattern even if the exact path has not been pre-generated during the initial build phase.

In production, however, dynamic routes need to be pre-rendered, either completely at build time with getStaticPaths in SSG projects or on-demand when needed using fallback behavior. Next.js builds each individual path returned by getStaticPaths, while fallback routes will either return a 404 page (if fallback is false) or render the page on the server for the first visitor (if fallback is true or 'blocking'). For paths added later, after deployment in an SSG scenario with fallback enabled, a new build would be required to statically generate these pages.*