gatsby-node.js

/**
 * Implement Gatsby's Node APIs in this file.
 *
 * See: https://www.gatsbyjs.org/docs/node-apis/
 */

// You can delete this file if you're not using it

const path = require(`path`)

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

  const blogPost = path.resolve(`./src/templates/blog-post-contentful.js`)
  return graphql(
    `
      {
        allContentfulPost {
            edges {
                node {
                    slug
                    title
                }
            }
        }
      }
    `
  ).then(result => {
    if (result.errors) {
      throw result.errors
    }

    // Create blog posts pages.
    const posts = result.data.allContentfulPost.edges

    posts.forEach((post, index) => {
      const previous = index === posts.length - 1 ? null : posts[index + 1].node
      const next = index === 0 ? null : posts[index - 1].node

      createPage({
        path: post.node.slug,
        component: blogPost,
        context: {
          slug: post.node.slug,
          previous,
          next,
        },
      })
    })

    return null
  })
}