recursivewalkP.js

walk([dir, []])
  .then(all => console.log('all', all))
  .catch(err => console.error('err', err))

function readdir(directory) {
  return new Promise((accept, reject) => {
    fs.readdir(directory, (err, files) => {
      if (err) reject(err)
      accept(files)
    })
  })
}

function stat(file, results) {
  return new Promise((accept, reject) => {
    fs.stat(file, (err, stats) => {
      if (err || stats && !stats.isDirectory()) {
        results.push(file)
        return reject(err)
      }
      return accept([file, results])
    })
  })
}


function walk(args) {
  const dir = args[0]
  const results = args[1]

  return readdir(dir)
    .then((files) => {
      const filesP = files.map(f => {
        const file = path.resolve(dir, f)
        return stat(file, results)
          .then(walk)
          .catch(x => x)
      })

      return Promise.all(filesP)
    })
    .then(() => results)
}