Coffeescript that finds files with extensions using the async library

findFileWithExtension.js

var findFilesWithExtension,
  _this = this;

findFilesWithExtension = function(dir, extensions, callback) {
  var directories, files;
  files = [];
  directories = [dir];
  return async.whilst(function() {
    return directories.length > 0;
  }, function(whilstCallback) {
    var directory;
    directory = directories.pop();
    return fs.readdir(directory, function(err, fileList) {
      var f, stats, _i, _len;
      for (_i = 0, _len = fileList.length; _i < _len; _i++) {
        f = fileList[_i];
        f = directory + '/' + f;
        stats = fs.statSync(f);
        if (stats.isFile()) {
          files.push(f);
        } else if (stats.isDirectory()) {
          directories.push(f);
        }
      }
      return whilstCallback();
    });
  }, function(err) {
    if (err) throw err;
    return async.filter(files, function(file, filterCallback) {
      return async.detect(extensions, function(extension, detectCallback) {
        return detectCallback(~file.indexOf(extension));
      }, function(result) {
        return filterCallback(result);
      });
    }, function(results) {
      return callback(results);
    });
  });
};

findFileWtithExtension.coffee

findFilesWithExtension = (dir, extensions, callback) =>
  files = []
  directories = [dir]
  
  async.whilst () =>
    directories.length > 0
  , (whilstCallback) =>
    directory = directories.pop()
    fs.readdir directory, (err, fileList) =>
      for f in fileList
        f = directory + '/' + f
        stats = fs.statSync f
        if stats.isFile()
          files.push f
        else if stats.isDirectory()
          directories.push f
      
      whilstCallback()
  , (err) =>
    if err
      throw err
    async.filter files, (file, filterCallback) =>
        async.detect extensions, (extension, detectCallback) =>
          detectCallback ~file.indexOf extension
        , (result) =>
          filterCallback result
    , (results) =>
      callback(results)

usage.coffee

findFilesWithExtension "static", [".js"], (files) =>
  # Do something with the filtered files
  console.log files