gatsby-node.js

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

// You can delete this file if you're not using it

const path = require(`path`)
const _ = require('lodash')
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: `blogs` })
    createNodeField({
      node,
      name: `slug`,
      value: slug,
    })
  }
}

exports.createPages = ({ graphql, actions }) => {
  const { createPage } = actions
  const blogPostTemplate = path.resolve('./src/templates/blog-post.tsx')
  const tagTemplate = path.resolve('./src/templates/tags.tsx')

  return graphql(`
    {
      allMarkdownRemark(filter: { frontmatter: { draft: { ne: true } } }) {
        edges {
          node {
            fields {
              slug
            }
            frontmatter {
              title
              tags
            }
          }
        }
      }
    }
  `).then((result) => {
    const posts = result.data.allMarkdownRemark.edges

    posts.forEach(({ node }) => {
      createPage({
        path: node.fields.slug,
        component: blogPostTemplate,
        context: {
          // Data passed to context is available
          // in page queries as GraphQL variables.
          slug: node.fields.slug,
        },
      })
    })

    let tags = []
    // Iterate through each post, putting all found tags into `tags`
    _.each(posts, (edge) => {
      if (_.get(edge, 'node.frontmatter.tags')) {
        tags = tags.concat(edge.node.frontmatter.tags)
      }
    })
    // Eliminate duplicate tags
    tags = _.uniq(tags)

    // Make tag pages
    tags.forEach((tag) => {
      createPage({
        path: `/tags/${_.kebabCase(tag)}/`,
        component: tagTemplate,
        context: {
          // Data passed to context is available
          // in page queries as GraphQL variables.
          tag,
        },
      })
    })
  })
}