gatsby-node.js

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

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

  return graphql(`
    {
      allMarkdownRemark(limit: 1000) {
        edges {
          node {
            id
            fields {
              slug
            }
            frontmatter {
              path
              templateKey
            }
          }
        }
      }
    }
  `).then(result => {
    if (result.errors) {
      result.errors.forEach(e => console.error(e.toString()));
      return Promise.reject(result.errors);
    }

    // Filter out the footer, navbar, and meetups so we don't create pages for those
    const postOrPage = result.data.allMarkdownRemark.edges.filter(edge => {
      if (edge.node.frontmatter.templateKey === 'navbar') {
        return false;
      } else if (edge.node.frontmatter.templateKey === 'footer') {
        return false;
      } else {
        return !Boolean(edge.node.fields.slug.match(/^\/meetups\/.*$/));
      }
    });

    postOrPage.forEach(edge => {
      let component, pathName;
      if (edge.node.frontmatter.templateKey === 'home-page') {
        pathName = '/';
        component = path.resolve(`src/pages/index.js`);
      } else {
        pathName = edge.node.frontmatter.path || edge.node.fields.slug;
        component = path.resolve(
          `src/templates/${String(edge.node.frontmatter.templateKey)}.js`
        );
      }
      const id = edge.node.id;
      createPage({
        path: pathName,
        component,
        // additional data can be passed via context
        context: {
          id
        }
      });
    });
  });
};

exports.onCreateWebpackConfig = ({ getConfig, stage }) => {
  const config = getConfig();
  if (stage.startsWith('develop') && config.resolve) {
    config.resolve.alias = {
      ...config.resolve.alias,
      'react-dom': '@hot-loader/react-dom'
    };
  }
};

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

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