gatsby-node.js

const path = require('path')
const _ = require('lodash')
const webpackLodashPlugin = require('lodash-webpack-plugin')

exports.onCreateNode = ({ node, boundActionCreators, getNode }) => {
  const { createNodeField } = boundActionCreators
  let slug
  if (node.internal.type === 'MarkdownRemark') {
    const fileNode = getNode(node.parent)
    const parsedFilePath = path.parse(fileNode.relativePath)
    if (
      Object.prototype.hasOwnProperty.call(node, 'frontmatter') &&
      Object.prototype.hasOwnProperty.call(node.frontmatter, 'title')
    ) {
      slug = `/${_.kebabCase(node.frontmatter.title)}`
    } else if (parsedFilePath.name !== 'index' && parsedFilePath.dir !== '') {
      slug = `/${parsedFilePath.dir}/${parsedFilePath.name}/`
    } else if (parsedFilePath.dir === '') {
      slug = `/${parsedFilePath.name}/`
    } else {
      slug = `/${parsedFilePath.dir}/`
    }
    if (
      Object.prototype.hasOwnProperty.call(node, 'frontmatter') &&
      Object.prototype.hasOwnProperty.call(node.frontmatter, 'slug')
    ) {
      slug = `/${_.kebabCase(node.frontmatter.slug)}`
    }
    createNodeField({ node, name: 'slug', value: slug })
  }
}

exports.createPages = () => {}

exports.modifyWebpackConfig = ({ config, stage }) => {
  if (stage === 'build-javascript') {
    config.plugin('Lodash', webpackLodashPlugin, null)
  }
  if (stage === 'build-html') {
    config.loader('null', {
      test: /react-image-lightbox/,
      loader: 'null-loader',
    })
  }
}