gistfile1.txt

// Takes any async lib that uses callback based signatures and converts
// the specified names to continuable style and returns the new library.
exports.convert = function (lib, names) {
  var newlib = {};
  Object.keys(lib).forEach(function (key) {
    if (names.indexOf(key) < 0) {
      return newlib[key] = lib[key];
    }
    newlib[key] = function () {
      var args = Array.prototype.slice.call(arguments);
      return function (callback, errback) {
        args.push(function (err, val) {
          if (err) {
            errback(err);
          } else {
            callback(val);
          }
        });
        lib[key].apply(lib, args)
      }
    }
  });
  return newlib;
}

// usage
var fs = Do.convert(require('fs'), ['readdir', 'stat', 'readFile', 'writeFile']);