gatsby-node.js

const path = require(`path`)

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

  const loadPosts = new Promise((resolve, reject) => {
    graphql(`
      {
        allContentfulPost {
          edges {
            node {
              slug
            }
          }
        }
      }
    `).then(result => {
      result.data.allContentfulPost.edges.map(({ node }) => {
        createPage({
          path: `blog/${node.slug}/`,
          component: path.resolve(`./src/templates/post.js`),
          context: {
            slug: node.slug,
          },
        })
      })
      resolve()
    })
  })

  const loadGalleries = new Promise((resolve, reject) => {
    graphql(`
      {
        allContentfulGallery {
          edges {
            node {
              slug
            }
          }
        }
      }
    `).then(result => {
      result.data.allContentfulGallery.edges.map(({ node }) => {
        createPage({
          path: `${node.slug}/`,
          component: path.resolve(`./src/templates/gallery.js`),
          context: {
            slug: node.slug,
          },
        })
      })
      resolve()
    })
  })

  const loadTags = new Promise((resolve, reject) => {
    graphql(`
      {
        allContentfulTag {
          edges {
            node {
              slug
            }
          }
        }
      }
    `).then(result => {
      result.data.allContentfulTag.edges.map(({ node }) => {
        createPage({
          path: `tag/${node.slug}/`,
          component: path.resolve(`./src/templates/tag.js`),
          context: {
            slug: node.slug,
          },
        })
      })
      resolve()
    })
  })

  return Promise.all([loadPosts, loadGalleries, loadTags])
}