Previous and Next Post using Next.js

I spent weeks trying to figure this out, I am not going to make you go through the same. Let’s get straight into it…

The Problem

On a Next.js site with posts fetched via graphql, how would you implement Previous and Next POST. This would be on the detail view of a post.

The Solution

The solution below uses graphql and Contentful but can be modified to wherever you want to apply it.

const ARTICLE_QUERY = `
query {
    articleCollection(order: publishedAt_DESC) {
      items {
        slug
        title
        excerpt
        category {
          title
          categorySlug
        }
        series {
          title
          slug
        }
        body {
          json
        }
      }
    }
  }
  
`;

async function fetchGraphQL(query) {
  return fetch(
    `https://graphql.contentful.com/content/v1/spaces/${process.env.SPACE_ID}`,
    {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        Authorization: `Bearer ${process.env.CDA_TOKEN}`,
      },
      body: JSON.stringify({ query }),
    }
  )
    .then((response) => response.json())
    .catch((error) => console.error(error));
}

export async function getPostAndMorePosts(slug) {
  const response = await fetchGraphQL(ARTICLE_QUERY);
  const posts = response.data.articleCollection.items;

  const currentPost = posts.find((post) => post.slug === slug);
  const currentPostIndex = posts.findIndex((post) => post.slug === slug);
  const prevPost = posts[currentPostIndex - 1] || posts[posts.length - 1];
  const nextPost = posts[currentPostIndex + 1] || posts[0];

  if (!currentPost) {
    return {
      post: false,
    };
  }

  return {
    post: currentPost,
    morePosts: [prevPost, nextPost],
  };
}

In the code above:

• We create the article query and make a function to perform our query - fetchGraphQL
• We then export an async function getPostAndMorePosts that takes slug as a parameter. In it, we use fetchGraphQL to get all our posts as an array.
• We use find to get the post with the slug that matches the passed slug parameter - currentPost
• Using currentPost as an index, we get the post before and the post after - these become our previous post and next post respectively
• Lastly, return currentPost as post and morePosts as an array of the previous and next post.

in [slug].js:

import getPostAndMorePosts from '../../lib/api'

export async function getStaticPaths() {
  ...
}

export async function getStaticProps({ params }) {
  const data = await getPostAndMorePosts(params.slug);

  return {
    props: {
      post: data?.post ?? null,
      morePosts: data?.morePosts ?? null,
    },
  };
}

export default function Post({ post, morePosts }) {
	...
}

In our dynamic page:

• We import getPostAndMorePosts - we will use it in getStaticProps after we pass the params from getStaticPaths.
• In getStaticProps, we pass params.slug to getPostAndMorePosts to get:
  • The current post data
  • The previous and next post data
• Lastly, we pass this data to our component and render our data.

Here is the repo with the full implementation: https://github.com/stefanjudis/jamstack-workshop/blob/main/lib/api.js

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Conclusion

Thank you whitep4nth3r, Thank you to everyone who tried to help.

The full story of how we got here is coming in another article. It really puzzles me how there isn’t a native solution for this. Gatsby has it, WordPress does as well. What happened here Next.js?

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Thank you for reading, let’s connect!

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