gatsby-node.js

const path = require('path');

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

  return graphql(`
    {
      allMarkdownRemark(sort: { order: DESC, fields: [frontmatter___date] }, limit: 1000) {
        edges {
          node {
            excerpt(pruneLength: 400)
            html
            id
            frontmatter {
              templateKey
              path
              date
              title
              aboutData {
                paragraph
              }
            }
          }
        }
      }
    }
  `).then(result => {
    if (result.errors) {
      return Promise.reject(result.errors);
    }
    result.data.allMarkdownRemark.edges.forEach(({ node }) => {
      createPage({
        path: node.frontmatter.path,
        component: path.resolve(`src/templates/${String(node.frontmatter.templateKey)}.js`),
        context: {} // additional data can be passed via context
      });
    });
  });
};