list all files in a recursive way

scandir.js

module.exports = function scandir (dir, cb) {
  const fs = require('fs')
  const path = require('path')
  let result = []

  fs.readdir(dir, (err, filesList) => {
    if (err) return cb(err)
    let pending = filesList.length
    if (!pending) return cb(null, result)

    filesList.forEach((file) => {
      file = path.resolve(dir, file)

      fs.stat(file, (err, stat) => {
        if (stat && stat.isDirectory()) {
          scandir(file, (err, res) => {
            if (err) cb(err)
            result = result.concat(res)
            if (!--pending) cb(null, result)
          })
        } else {
          result.push(file)
          if (!--pending) cb(null, result)
          
          /* extention filtering
          let extentions = ['.mkv', '.MKV', '.mp4', '.MP4', '.avi', '.AVI', '.flv', '.FLV']
          for (let extention of extentions) {
            if (file.endsWith(extention)) result.push(file)
          }
          */
        }
      })
    })
  })
}