walkIn.js

import { resolve } from 'path';
import fs from 'fs/promises';

async function walkIn(inputPath) {
  const ls = await fs.readdir(inputPath, { withFileTypes: true });
  const files = await Promise.all(ls.map((dirent) => {
    const res = resolve(inputPath, dirent.name);
    return dirent.isDirectory() ? walkIn(res) : res;
  }));
  return [].concat(...files);
}

(async function () {
  const res = await walkIn('../');
  console.log(res);
})();