gatsby-node.js

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

exports.onCreateWebpackConfig = ({ actions, loaders, stage }) => {
  if (stage === "build-html") {
    actions.setWebpackConfig({
      module: {
        rules: [
          {
            test: /docsearch\.js/,
            use: loaders.null()
          },
          {
            test: /firebase/,
            use: loaders.null()
          }
        ]
      }
    });
  }
};
exports.createPages = ({ actions, graphql }) => {
  const { createPage } = actions;

  return graphql(`
    {
      allMarkdownRemark(filter: { fileAbsolutePath: { glob: "**/blog/**" } }) {
        edges {
          node {
            id
            fileAbsolutePath
          }
        }
      }
    }
  `)
    .then(result => {
      if (result.errors) {
        result.errors.forEach(e => console.error(e.toString()));
        return Promise.reject(result.errors);
      }

      const posts = result.data.allMarkdownRemark.edges;
      const regex = /.*\/blog\/(\d{4})-(\d{2})-(\d{2})-(.*)\.md/i;
      posts.forEach(edge => {
        const id = edge.node.id;
        createPage({
          path: edge.node.fileAbsolutePath.replace(regex, "/blog/$1/$2/$3/$4"),
          component: path.resolve(`src/templates/blog.js`),
          // additional data can be passed via context
          context: {
            id
          }
        });
      });
    })
    .then(() =>
      graphql(`
        {
          allMarkdownRemark(
            filter: { fileAbsolutePath: { glob: "**/docs/**" } }
          ) {
            edges {
              node {
                id
                fields {
                  slug
                }
              }
            }
          }
        }
      `)
    )
    .then(result => {
      if (result.errors) {
        result.errors.forEach(e => console.error(e.toString()));
        return Promise.reject(result.errors);
      }
      const posts = result.data.allMarkdownRemark.edges;
      posts.forEach(edge => {
        const id = edge.node.id;
        createPage({
          path: edge.node.fields.slug,
          component: path.resolve(`src/templates/docs.js`),
          // additional data can be passed via context
          context: {
            id
          }
        });
      });
    });
};

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

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