gatsby-node.js

const path = require('path')

exports.createPages = async ({ graphql, actions, reporter }) => {
  const { createPage } = actions

  const result = await graphql(`
    query {
      allMdx(sort: {order: DESC, fields: frontmatter___date}) {
        edges {
          node {
            id
            frontmatter {
              slug,
              title
              coverAlt
              cover {
                childImageSharp {
                  gatsbyImageData(
                    layout: CONSTRAINED
                    placeholder: BLURRED
                    formats: [AUTO, WEBP, AVIF]
                  )
                }
              }
            }
          }
        }
      }
    }
  `)

  if (result.errors) {
    reporter.panicOnBuild('🚨  ERROR: Loading "createPages" query')
  }

  const posts = result.data.allMdx.edges

  posts.forEach(({ node }, index) => {
    createPage({
      path: node.frontmatter.slug,
      component: path.resolve(`./src/modules/layout/PostLayout.jsx`),
      context: {
        id: node.id,
        postIndex: index,
        prev: index === 0 ? null : posts[index - 1].node,
        next: index === posts.length - 1 ? null : posts[index + 1].node
      },
    })
  })
}