(function () {

  'use strict';

  function Obj() {

    this.a = 12;

    this.b = "a";

    this.privilegedMethod = function () {

      this.a++;

      privateMethod.bind(this)();

      return this;

    };

​

    function privateMethod() {

      this.b = "foo";

      return this;

    }

    return this;

  }

  var obj = new Obj();

​

  console.log(obj.privilegedMethod().b);

}());

​