gatsby-node.js

const path = require('path')
const { createFilePath } = require('gatsby-source-filesystem')

const createBlogIndexPages = (createPage, posts) => {
  // Create blog index pages
  const postsPerPage = 5
  const pageCount = Math.ceil(posts.length / postsPerPage)
  const blogIndexTemplate = path.resolve('./src/templates/blog-index.js')

  Array.from({ length: pageCount }).forEach((_, i) => {
    createPage({
      path: i === 0 ? '/' : `/page/${i + 1}`,
      component: blogIndexTemplate,
      context: {
        limit: postsPerPage,
        skip: i * postsPerPage,
        pageCount,
        currentPage: i + 1,
      },
    })
  })
}

const createBlogTitlesPage = (createPage) => {
  // Create blog titles page
  const blogTitlesTemplate = path.resolve('./src/templates/blog-titles.js')

  createPage({
    path: '/posts',
    component: blogTitlesTemplate,
  })
}

const createBlogPostPages = (createPage, posts) => {
  // Create blog posts pages
  const blogPostTemplate = path.resolve('./src/templates/blog-post.js')

  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.fields.slug,
      component: blogPostTemplate,
      context: {
        slug: post.node.fields.slug,
        previous,
        next,
      },
    })
  })
}

const createAboutPage = (createPage) => {
  const blogAboutTemplate = path.resolve('./src/templates/blog-about.js')

  createPage({
    path: '/about',
    component: blogAboutTemplate,
  })
}

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

  const blogQuery = await graphql(
    `
      {
        allMarkdownRemark(
          filter: { fileAbsolutePath: { regex: "/blog/" } }
          sort: { frontmatter: { date: DESC } }
          limit: 1000
        ) {
          edges {
            node {
              fileAbsolutePath
              fields {
                slug
              }
              frontmatter {
                title
              }
            }
          }
        }
      }
    `,
  )

  const posts = blogQuery.data.allMarkdownRemark.edges

  createBlogIndexPages(createPage, posts)
  createBlogTitlesPage(createPage)
  createBlogPostPages(createPage, posts)
  createAboutPage(createPage)

  return null
}

exports.onCreateNode = ({ node, actions, getNode }) => {
  const { createNodeField } = actions

  if (node.internal.type === 'MarkdownRemark') {
    const value = createFilePath({ node, getNode })
    createNodeField({
      name: `slug`,
      node,
      value,
    })
  }
}