Javascript private functions

private.js

// Reference: http://javascript.crockford.com/private.html

Test = function() {
  function private() {
    return "private";
  }
  return {
    public: function() {
      return private();
    }
  }
}

Test().public();  // "private"
Test().private();  // TypeError: Object #<Object> has no method 'private'


// Object-oriented style
Example = {};

(function(namespace) {
  function User(params) {
    this.name = params.name;
    this.birthday = params.birthday;
  }

  User.prototype = {
    firstName: function() {
      return this.name.replace(/ .*/, "");
    },

    age: function() {
      return Math.floor(yearsBetween(this.birthday, new Date()));
    }
  }

  var yearsBetween = function(startDate, endDate) {
    var ms = endDate - startDate;
    return ms / (1000*60*60*24*365);
  }

  namespace.User = User;
})(Example);

var user = new Example.User({name: "John Doe", birthday: new Date(1981, 1, 14)});
user.name;  // "John Doe"
user.birthday;  // Sat Feb 14 1981 00:00:00 GMT-0300 (BRST)
user.firstName();  // "John"
user.age();  // 32

// No way to access "yearsBetween" function
user.yearsBetween(user.birthday, new Date());  // TypeError: Object #<Object> has no method 'yearsBetween'
Example.User.yearsBetween(user.birthday, new Date());  // TypeError: Object function User(params) { this.name = params.name; this.birthday = params.birthday; } has no method 'yearsBetween'
Example.yearsBetween(user.birthday, new Date());  // TypeError: Object #<Object> has no method 'yearsBetween'