docs/middleware/categories-for-support.js

const path = require('path')
const renderOpts = { textOnly: true, encodeEntities: true }

// This middleware exposes a list of all categories and child articles at /categories.json.
// GitHub Support uses this for internal ZenDesk search functionality.
module.exports = async function categoriesForSupport (req, res, next) {
  const englishSiteTree = req.context.siteTree.en

  const allCategories = []

  await Promise.all(Object.keys(englishSiteTree).map(async (version) => {
    await Promise.all(englishSiteTree[version].childPages.map(async (productPage) => {
      if (productPage.page.relativePath.startsWith('early-access')) return
      if (!productPage.childPages) return

      await Promise.all(productPage.childPages.map(async (categoryPage) => {
        // We can't get the rendered titles from middleware/render-tree-titles
        // here because that middleware only runs on the current version, and this
        // middleware processes all versions.
        const name = categoryPage.page.title.includes('{')
          ? await categoryPage.page.renderProp('title', req.context, renderOpts)
          : categoryPage.page.title

        allCategories.push({
          name,
          published_articles: await findArticlesPerCategory(categoryPage, [], req.context)
        })
      }))
    }))
  }))

  return res.json(allCategories)
}

async function findArticlesPerCategory (currentPage, articlesArray, context) {
  if (currentPage.page.documentType === 'article') {
    const title = currentPage.page.title.includes('{')
      ? await currentPage.page.renderProp('title', context, renderOpts)
      : currentPage.page.title

    articlesArray.push({
      title,
      slug: path.basename(currentPage.href)
    })
  }

  if (!currentPage.childPages) return articlesArray

  // Run recursively to find any articles deeper in the tree.
  await Promise.all(currentPage.childPages.map(async (childPage) => {
    await findArticlesPerCategory(childPage, articlesArray, context)
  }))

  return articlesArray
}