// Promises

const { promises: { readdir } } = require('fs')

const getDirectories = async source =>
  (await readdir(source, { withFileTypes: true }))
    .filter(dirent => dirent.isDirectory())
    .map(dirent => dirent.name)
    
 // Synchronous
 const { readdirSync } = require('fs')

const getDirectories = source =>
  readdirSync(source, { withFileTypes: true })
    .filter(dirent => dirent.isDirectory())
    .map(dirent => dirent.name)
    
 // Callbacks
 const { readdir } = require('fs')

const getDirectories = (source, callback) =>
  readdir(source, { withFileTypes: true }, (err, files) => {
    if (err) {
      callback(err)
    } else {
      callback(
        files
          .filter(dirent => dirent.isDirectory())
          .map(dirent => dirent.name)
      )
    }
  })