gatsby-node.js

const path = require(`path`);

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

  const postTemplate = path.resolve(`./src/templates/template.js`);

  return graphql(
    `
      {
        allMarkdownRemark(
          sort: { fields: [frontmatter___date], order: DESC }
          limit: 1000
        ) {
          edges {
            node {
              fields {
                slug
              }
              frontmatter {
                title
                category
                draft
              }
            }
          }
        }
      }
    `
  ).then(result => {
    if (result.errors) {
      throw result.errors;
    }

    // Create blog posts pages.
    const posts = result.data.allMarkdownRemark.edges.filter(
      ({ node }) => !node.frontmatter.draft && !!node.frontmatter.category
    );

    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: postTemplate,
        context: {
          slug: post.node.fields.slug,
          previous,
          next,
        },
      });
    });
  });
};

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

  if (node.internal.type === `MarkdownRemark`) {
    const value = path.basename(node.fileAbsolutePath, '.md');
    createNodeField({
      name: `slug`,
      node,
      value,
    });
  }
};

exports.onCreateWebpackConfig = ({ actions }) => {
  actions.setWebpackConfig({
    resolve: {
      alias: {
        '@': path.resolve(__dirname, 'src'),
        '@static': path.resolve(__dirname, 'static'),
        '@content': path.resolve(__dirname, 'content'),
      },
    },
  });
};