Next.js Parallel Routes

Introduction

Next.js provides an easy way to create dynamic and asynchronous server-rendered pages using React. Parallel Routes is one such feature of Next.js that enables faster server rendering by simultaneously fetching data from multiple routes. In this article, we'll explore how Parallel Routes work and how to implement them in Next.js projects.

Syntax

The syntax to implement Parallel Routes in Next.js is as follows:

export async function getStaticProps() {
  const [users, posts, comments] = await Promise.all([
    fetch('/api/users'),
    fetch('/api/posts'),
    fetch('/api/comments')
  ]);
  return {
    props: {
      users: await users.json(),
      posts: await posts.json(),
      comments: await comments.json()
    }
  };
}

Example

Here's how to implement Parallel Routes in a Next.js project:

import Link from 'next/link'

export async function getStaticPaths() {
  const users = await fetch('/api/users')
  const usersData = await users.json()
  const paths = usersData.map((user) => ({
    params: { userId: user.id.toString() },
  }))
  return { paths, fallback: false }
}

export async function getStaticProps({ params }) {
  const [user, posts] = await Promise.all([
    fetch(`/api/users/${params.userId}`),
    fetch(`/api/posts?userId=${params.userId}`),
  ])
  const userData = await user.json()
  const postsData = await posts.json()
  return {
    props: {
      user: userData,
      posts: postsData
    }
  }
}

function UserDetails({ user, posts }) {
  return (
    <div>
      <h1>{user.name}</h1>
      <p>{user.email}</p>
      <h2>Posts</h2>
      <ul>
        {posts.map(post => (
          <li key={post.id}>{post.title}</li>
        ))}
      </ul>
      <Link href="/users">
        <a>Back to Users</a>
      </Link>
    </div>
  )
}

export default UserDetails

Output

The output will be a user details page with the user's name, email, and a list of their posts. By fetching data from multiple routes simultaneously, the page load will be much faster than it would be if each route was fetched one at a time.

Explanation

In the above example, we have used the getStaticPaths method to fetch the list of users from the /api/users route and generate a list of dynamic paths based on their userId. Then we have used the getStaticProps method to fetch the data for a specific user from the /api/users route and their posts from the /api/posts route using Promise.all to execute the requests in parallel. The fetched data is then passed as props to the UserDetails component, which uses it to render the user's details and their posts.

Use

Parallel Routes can be used in Next.js projects to speed up the server rendering of pages that require data from multiple routes. This can be particularly useful for pages that require a lot of data to be fetched and processed before they can be rendered.

Important Points

• Parallel Routes can significantly improve the performance of Next.js applications by fetching data from multiple routes simultaneously.
• Promise.all can be used to execute multiple requests in parallel and wait for all of them to complete before returning the data to the component.
• getStaticProps and getServerSideProps can be used to fetch data from multiple routes on the server, while useSWR can be used on the client-side to fetch data asynchronously.

Summary

Parallel Routes is a powerful feature of Next.js that allows for faster server rendering of pages that require data from multiple routes. By fetching data from multiple routes simultaneously, Next.js is able to speed up page loads and improve the overall user experience. By understanding how to implement this feature in your Next.js projects, you can take advantage of the performance benefits it provides.