gatsby-node.js

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

exports.onCreateWebpackConfig = ({ getConfig, stage }) => {
  const config = getConfig()
  if (stage.startsWith("develop") && config.resolve) {
    config.resolve.alias = {
      ...config.resolve.alias,
    }
  }
}

// To add the slug field to each post
exports.onCreateNode = ({ node, getNode, actions }) => {
  const { createNodeField } = actions

  if (node.internal.type === "MarkdownRemark") {
    const slug = createFilePath({
      node,
      getNode,
      basePath: "pages",
    })

    createNodeField({
      node,
      name: "slug",
      value: `/${slug.slice(12)}`,
    })
  }
}

// To create the posts pages
exports.createPages = ({ graphql, actions }) => {
  const { createPage } = actions

  return graphql(`
    {
      posts: allMarkdownRemark(
        sort: { frontmatter: { date: DESC } }
      ) {
        edges {
          node {
            fields {
              slug
            }
            frontmatter {
              category
              date(locale: "pt-br", formatString: "DD [de] MMMM [de] YYYY")
              description
              title
              image
            }
          }
          next {
            fields {
              slug
            }
            frontmatter {
              title
            }
          }
          previous {
            frontmatter {
              title
            }
            fields {
              slug
            }
          }
        }
      }
    }
  `).then(result => {
    const posts = result.data.posts.edges
    const postsPerPage = 6
    const numPages = Math.ceil(posts.length / postsPerPage)

    posts.forEach(({ node, next, previous }) => {
      createPage({
        path: node.fields.slug,
        component: path.resolve(`./src/templates/blog-post.js`),
        context: {
          slug: node.fields.slug,
          previousPost: next,
          nextPost: previous,
        },
      })
    })

    Array.from({ length: numPages }).forEach((_, index) => {
      createPage({
        path: index === 0 ? `/` : `/page/${index + 1}`,
        component: path.resolve(`./src/templates/blog-list.js`),
        context: {
          limit: postsPerPage,
          skip: index * postsPerPage,
          numPages,
          currentPage: index + 1,
        },
      })
    })
  })
}