readdirSync but recursive - also known as walkDirSync (concise glob alternative)

readdirSyncRecursive.js

const fs = require('fs');
const dir = (d) => fs.readdirSync(d, {withFileTypes:true})
  .map(f=>f.isDirectory() ? dir(d + '/' + f.name) : d + '/' + f.name)
  .flat();

// console.log(dir('somedir'));
// can use .filter() afterwards, of course

readdirSyncRecursive1.mjs

const fs = require('fs');
const path = require('path');

/**
* Also known as dirWalkSync.js
* returns array of string paths (ls -r, dir /s)
* includes both files an directories, these ones ending in 'path.sep'
*/
export function dirWalkSync (dir, filter, acc=[] ) {
  dir = Array.isArray(dir) ? path.join(...dir) : dir;

  for (let el of fs.readdirSync(dir, { withFileTypes: true })) {
    let elName = path.join(dir,el.name, el.isDirectory() ? path.sep : '')
    if ( !filter 
      || (typeof filter === 'object' && filter.test(elName))
      || (typeof filter === 'function' && filter(elName))
    ) { 
      acc.push(elName) 
    }
    if (el.isDirectory()) { 
      dirWalkSync(elName,filter,acc) 
    }
  }
  return acc;
}
dirWalkSync.sep = path.sep;  // so you dont have to import path just for this

// -- EXAMPLES
//console.log(dirWalkSync([__dirname,'.']).join('\n'))  // can pipe this in linux, e.g.
//console.log(dirWalkSync('.', /test\.js$/ ))
//console.log(dirWalkSync('.', e=>!e.match(/(\.git|node_modules)/) && e.endsWith(dirWalkSync.sep)));

readdirSyncRecursive2.js

/**
 * old version
 * Like readdirSync but recursive
 * opt:
 *    type:dir
 *    depth: n
 */
function readdirSyncRecursive2(folder, opt={depth:9999} ) {
 if (--opt.depth <=0) return []

  let fs = require('fs')
  let baseDir = folder.match(/\/$/) ? folder : folder + '/'
  let filesAndFolders = fs.readdirSync(baseDir).map( f=>baseDir+f )
	
  let files = []
  filesAndFolders.forEach( f=>{	
	  if (fs.statSync(f).isDirectory()) {
    if (opt.type === 'dir') files.push(f)
      files = files.concat( readdirSyncRecursive(f, Object.assign({},opt) ))	// clone opt object to prevent mess
    } else {
      if (opt.type !== 'dir') files.push(f)
    }
  })
  return files
}

readdirSyncRecursive_alternatives.md

// simple list files of a folder (not recursive)
const fs = require('fs');
const path = require('path');
let filesAndDirs = fs.readdirSync(path.join(__dirname,'/'));

// subdirectories only (not recursive)
let subdirs = fs.readdirSync(path.join(__dirname,'/')).filter(f=>fs.statSync(f).isDirectory());

// subdirectories only (node +10)
const fs = require('fs');
function getSubdirectories (baseDir) {
  return fs.readdirSync(baseDir, { withFileTypes: true })
    .filter(dirObj => dirObj.isDirectory())
    .map(dirObj => dirObj.name);
 }

// with glob, directories only (normal or recursive)
const glob = require('glob');   // npm install glob
let subdirs = glob.sync('__dirname',{mark:true}).filter(f=>f.endsWith('/'))   // mark adds '/' at the end of directories