walk.js

const fs = require("fs");
const path = require("path");
const walk = function (dir, done) {
  let results = [];
  fs.readdir(dir, function (err, list) {
    if (err) return done(err);
    let pending = list.length;
    if (!pending) return done(null, results);
    list.forEach(function (file) {
      file = path.resolve(dir, file);
      fs.stat(file, function (err, stat) {
        if (stat && stat.isDirectory()) {
          walk(file, function (err, res) {
            results = results.concat(res);
            if (!--pending) done(null, results);
          });
        } else {
          results.push(file);
          if (!--pending) done(null, results);
        }
      });
    });
  });
};

const walkPromisified = (dir) =>
  new Promise((resolve, reject) =>
    walk(dir, (err, res) => {
      if (err) {
        reject(err);
        return;
      }
      resolve(res);
    })
  );

module.exports = walkPromisified;