code: function walkDirRecursive(arr, currentDirPath) {
    fs.readdirSync(currentDirPath).forEach(function (name) {
      var filePath = path.join(currentDirPath, name);
      var stat = fs.statSync(filePath);
      if (stat.isDirectory()) {
        arr = walkDirRecursive(arr, filePath);
      } else {
        arr.push(filePath);
      }
    });
    return arr;
  }
docs: Recursively walks through and executes
  a callback function for each directory found.
  
  @param {String} currentDirPath
  @param {Function} callback
  @api private