[node.js 8+] Recursively get all files in a directory

getFiles.js

// Node 8+
// --------------------------------------------------------------
// No external dependencies

const { promisify } = require('util');
const { resolve } = require('path');
const fs = require('fs');
const readdir = promisify(fs.readdir);
const stat = promisify(fs.stat);

async function getFiles(dir) {
  const subdirs = await readdir(dir);
  const files = await Promise.all(subdirs.map(async (subdir) => {
    const res = resolve(dir, subdir);
    return (await stat(res)).isDirectory() ? getFiles(res) : res;
  }));
  return files.reduce((a, f) => a.concat(f), []);
}

// Usage

getFiles(__dirname)
  .then(files => console.log(files))
  .catch(e => console.error(e));


// Node 10.10+
// --------------------------------------------------------------
// Updated for node 10+ with even more whizbang:

const { resolve } = require('path');
const { readdir } = require('fs').promises;

async function getFiles(dir) {
  const dirents = await readdir(dir, { withFileTypes: true });
  const files = await Promise.all(dirents.map((dirent) => {
    const res = resolve(dir, dirent.name);
    return dirent.isDirectory() ? getFiles(res) : res;
  }));
  return Array.prototype.concat(...files);
}

// Note that starting with node 11.15.0 you can use 
// `files.flat()` instead of `Array.prototype.concat(...files)` 
// to flatten the array.


// Node 11+
// --------------------------------------------------------------
// The following version uses async iterators.

const { resolve } = require('path');
const { readdir } = require('fs').promises;

async function* getFiles(dir) {
  const dirents = await readdir(dir, { withFileTypes: true });
  for (const dirent of dirents) {
    const res = resolve(dir, dirent.name);
    if (dirent.isDirectory()) {
      yield* getFiles(res);
    } else {
      yield res;
    }
  }
}

// Usage has changed because the return type is now an 
// async iterator instead of a promise:

(async () => {
  for await (const f of getFiles('.')) {
    console.log(f);
  }
})()

// I've written more about async iterators here: 
// https://qwtel.com/posts/software/async-generators-in-the-wild/

@mrchief
Thanks! I got completely hung up on the resolve and missed the reference to the path module.
I'm trying to adapt this using a Mozilla Thunderbird DirectoryInterator as opposed to readDir.
I have been trying every possible combination of promise handling , but I am obviously flummoxed.
Removing the unnecessary path combination in my case still fails.
I'm going to keep experimenting but I may post my best if I can't get it. This approach is certainly what I need to use just with some tweaks that Confound me.