closure_constructor.js

var Animal = function() {
  var _name;
  this.animalType;
  this.setName = function(name) {
    _name = name;
  };
  this.getName = function() {
    return _name;
  };
};

var myCat = new Animal();
myCat.setName("Mr. Jones");
myCat.animalType = "cat";
myCat.animalType; // => "cat"
myCat.getName();  // => "Mr. Jones"
myCat._name; // => undefined