async/await + recursion = concise and highly expressive async code

directories-crawler.js

/* 
Crawl a directory and return a list containing all subdirectories paths 
*/

const fs = require('fs-extra');
const { promisify } = require('util');
const { resolve } = require('path');
const EventEmitter = require('events');

const isDir = folder => fs.lstatSync( folder ).isDirectory();
const listDir = path => promisify( fs.readdir )( resolve( path ) )

const getFoldersFromList = ( filesList, baseFolder ) =>
    filesList
        .map( file => `${baseFolder}/${file}`)
        .filter( folderPath => isDir( folderPath ) )

async function foldersCrawler( folder, accumulator = [] ) {
    try {
        let foldersList = getFoldersFromList( await listDir( folder ), folder );
        if( foldersList.length ) accumulator.push( ...foldersList );
        await Promise.all(
            foldersList
                .map( folderPath => foldersCrawler( folderPath , accumulator ) )
        );
        return accumulator;
    } catch(err) {
        throw err;
    }
}  

module.exports = async function listFolders(basePath) {
    try {
        return await foldersCrawler( basePath );
    } catch(err) {
        throw err;
    }
}