gatsby-node.js

/**
 * Implement Gatsby's Node APIs in this file.
 *
 * See: https://www.gatsbyjs.org/docs/node-apis/
 */

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

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

  if (node.internal.type === 'MarkdownRemark') {
    const slug = createFilePath({ node, getNode, basePath: 'markdown' })
    var slugNoSlash = slug.substr(0, slug.length - 1)
    createNodeField({
      node,
      name: 'slug',
      value: 'docs' + slugNoSlash,
    })
  }
}

exports.createPages = ({ graphql, actions }) => {
  const { createPage } = actions
  return new Promise((resolve, reject) => {
    graphql(`
      {
        allMarkdownRemark {
          edges {
            node {
              fields {
                slug
              }
            }
          }
        }
      }
    `).then(result => {
      result.data.allMarkdownRemark.edges.forEach(({ node }) => {
        createPage({
          path: node.fields.slug,
          component: path.resolve(`./src/templates/docs.js`),
          context: {
            // Data passed to context is available
            // in page queries as GraphQL variables.
            slug: node.fields.slug,
          },
        })
      })
      resolve()
    })
  })
}