docs/middleware/contextualizers/rest.js

const path = require('path')
const rest = require('../../lib/rest')
const removeFPTFromPath = require('../../lib/remove-fpt-from-path')

module.exports = function restContext (req, res, next) {
  req.context.rest = rest

  // link to include in `Works with GitHub Apps` notes
  // e.g. /ja/rest/reference/apps or /en/enterprise/2.20/user/rest/reference/apps
  req.context.restGitHubAppsLink = removeFPTFromPath(path.join(
    '/',
    req.context.currentLanguage,
    req.context.currentVersion,
    '/developers/apps'
  ))

  // ignore requests to non-REST reference paths
  if (!req.pagePath.includes('rest/reference')) return next()

  // e.g. the `activity` from `/en/rest/reference/activity#events`
  const category = req.pagePath
    .split('rest/reference')[1]
    .replace(/^\//, '') // remove leading slash
    .split('/')[0]

  // ignore empty strings or bare `/`
  if (!category || category.length < 2) return next()

  const operationsForCurrentProduct = req.context.rest.operations[req.context.currentVersion] || []

  // find all operations with a category matching the current path
  req.context.currentRestOperations = operationsForCurrentProduct.filter(operation => operation.category === category)

  return next()
}