async_r.js

// Asynchronously recursively reads files
function RecursiveReader(pathName, callback) {
  this.filesLeft = 1;
  this.pathName = pathName;
  this.callback = callback;
  this.data = '';
  this.readAll(this.pathName);
}

RecursiveReader.prototype = {
  readAll: function(pathName) {
    var rr = this;
    fs.readdir(pathName, function(err, files) {
      rr.filesLeft -= 1;
      rr.filesLeft += files.length;
      files.forEach(function(fileName) {
        fileName = path.join(pathName, fileName);
        fs.stat(fileName, function(err, stats) {
          if (stats && stats.isDirectory()) {
            return rr.readAll(fileName);
          } else {
            fs.readFile(fileName, function(err, contents) {
              rr.data += contents;
              rr.filesLeft -= 1;
              if (rr.filesLeft === 0) {
                rr.callback(rr.data);
              }
            });
          }
        });
      });
    });
  }
}