module.js

// simple prototypical module

(function() {
  
  // module namespace and version
  abc = { version: "0.0.1" }; 
  
  // abc.q() is the constructor
  abc.q = function (s){ 
    
    // the value of s is saved in x which
    // has a private scope in this closure
    var x = s
    
    // create an empty q object to add 
    // public functions to as properties
    var q = {};
    
    // public instance functions
    q.set = function(val) {
      x =  val
    }; 
    q.get = function(){
      return x
    };
    q.d = function(){
      return twotimes()
    };
    q.r = function() {
      q.set(Math.floor(Math.random()*10));
      return q.get();
    };
    
    // private functions
    function twotimes(){
      return x + x
    };
    
    // return the q object with the public
    // functions as properties
    return q
  }; 
})();

// abc.version     => '0.0.1'
// f = abc.q(4)
// g = abc.q(5)
// f.get()         => 4
// g.get()         => 5
// f.d()           => 8
// f.set(6)
// f.get()        => 12
// g.get()         => 5

//  References:
// http://www.adequatelygood.com/2010/3/JavaScript-Module-Pattern-In-Depth