gistfile1.txt

var Thing = module.exports = function (options) {
  for (var o in options) {
    this[o] = options[o];
  }
}

Thing.prototype.method = function (arg) {
  var self = this;
  self.property = 'word';
  fs.readFile('/root/something', function (err, data) {
    console.log(self.property);
    //self is still good here, who knows what 'this' might be.
  });
}