closure problem

client.js

var rest = require('restler');

function Client(baseUrl) {
  if (this instanceof Client) {
    this.baseUrl = baseUrl;
  }
  else {
    return new Client(baseUrl);
  }
};

/*
 * Performs an HTTP get to the given path.
 * @param {string} path: the url to get
 * @param {object} data: the data to send
 * @param {function} callback: the callback to run on complete.
 *    if null it will run this.callback
 */
Client.prototype.get = function(path) {
  var self = this;
  return function() {
    rest.get(self.baseUrl + path).on('complete', this.callback);
  }
};

/*
 * Performs an HTTP post to the given path.
 * @param {string} path: the url to post to
 * @param {object} data: the data to send
 * @param {function} callback: the callback to run on complete.
 *    if null it will run this.callback
 */
Client.prototype.post = function(path, data, callback) {
  var self = this;
  var cb = callback;
  return function() {
    console.log(path);
    console.log(cb);
    rest.post(self.baseUrl + path, data).on('complete', cb || this.callback);
  }
};

/*
 * Performs an HTTP post to the given path.
 * @param {string} path: the url to post to
 * @param {object} data: the data to send
 * @param {function} callback: the callback to run on complete.
 *    if null it will run this.callback
 */
Client.prototype.put = function(path, data) {
  var self = this;
  return function() {
    rest.put(self.baseUrl + path, data).on('complete', this.callback);
  }
};

module.exports = Client;