gatsby-node.js

const path = require("path");

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

	const blogTemplate = path.resolve("src/templates/blog.js");
	const eventTemplate = path.resolve("src/templates/event.js");

	return graphql(
		`
			{
				allMarkdownRemark {
					edges {
						node {
							id
							frontmatter {
								slug
							}
						}
					}
				}
			}
		`
	).then((res) => {
		if (res.errors) {
			return Promise.reject(errors);
		}

		res.data.allMarkdownRemark.edges.map((element) => {
			let slug = element.node.frontmatter.slug;

			if (slug) {
				//create page for blog using template
				if (slug.includes(`/blog/`)) {
					createPage({
						path: slug,
						component: blogTemplate,
					});
				} else if (slug.includes(`/events/`)) {
					createPage({
						path: slug,
						component: eventTemplate,
					});
				}
			}
		});
	});
};