Example of a gatsby-node file

gatsby-node.js

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

	return new Promise((resolve, reject) => {
		graphql(
			`
        {
          allContentfulBlogPost {
            edges {
              node {
                id
                title
                slug
                category {
                  id
                  title
                }
              }
            }
          }
        }
      `
		)
			.then(result => {
				if (result.errors) {
						reject(result.errors)
					}

					const postTemplate = path.resolve('./src/templates/SinglePost/SinglePost.js')

					each(result.data.allContentfulBlogPost.edges, edge => {
						const slug = `/blog/${edge.node.slug}/`

						createPage({
							path: slug,
							component: slash(postTemplate),
							layout: `blog-layout`,
							context: {
								id: edge.node.id,
								slug,
								category: edge.node.category.id,
							},
						})
					})
          resolve()
			})