Expose private variables for unit testing in JavaScript

exposePriv.js

/* The code below takes a constructor and exposes its private functions
   Useful for unit testing (not general use). An example usage is below it. 
   Access to the private functions available through the _privMems property. */
/* Original credit goes to Rob Gravelle
   http://www.htmlgoodies.com/beyond/javascript/accessing-private-functions-in-javascript.html */

var Reflection = {};
 
Reflection.createExposedInstance = function(objectConstructor, args)
{
    // get the functions as a string
    var objectAsString    = objectConstructor.toString();
    var aPrivateFunctions = objectAsString.match(/function\s*?(\w.*?)\(/g);

    // To expose the private functions, we create
    // a new function that goes trough the functions string
    // we could have done all string parsing in this class and
    // only associate the functions directly with string
    // manipulation here and not inside the new class,
    // but then we would have to expose the functions as string
    // in the code, which could lead to problems in the eval since
    // string might have semicolons, line breaks etc.
    //INITIAL CODE
    /* var funcString = "new ("
                 + objectAsString.substring(0, objectAsString.length - 1)
                 + ";"
                 + "this._privMems = {};\n"
                 + "this._initPrivates = function(pf) {"
                 + "  this._privMems = {};"
                 + "  for (var i = 0, ii = pf.length; i < ii; i++)"
                 + "  {"
                 + "    var fn = pf[i].replace(/(function\\s+)/, '').replace('(', '');"
                 + "    try { "
                 + "      this._privMems[fn] = eval(fn);"
                 + "    } catch (e) {"
                 + "      if (e.name == 'ReferenceError') { continue; }"
                 + "      else { throw e; }"
                 + "    }"
                 + "  }"
                 + "}"
                 + "\n\n})()";

    var instance = eval(funcString);
    instance._initPrivates(aPrivateFunctions);
    */

    // SECOND TRY, WORKS WITH PROTOTYPE CHAIN
    /* var funcString = objectAsString.substring(0, objectAsString.length - 1)
             + ";"
             + "this.prototype=Object.create(objectConstructor.prototype);\n"
             + "this._privMems = {};\n"
             + "this._initPrivates = function(pf) {"
             + "  this._privMems = {};"
             + "  for (var i = 0, ii = pf.length; i < ii; i++)"
             + "  {"
             + "    var fn = pf[i].replace(/(function\\s+)/, '').replace('(', '');"
             + "    try { "
             + "      this._privMems[fn] = eval(fn);"
             + "    } catch (e) {"
             + "      if (e.name == 'ReferenceError') { continue; }"
             + "      else { throw e; }"
             + "    }"
             + "  }"
             + "}"
             + "\n\n}";
    eval("var OtherClass = "+funcString);
    OtherClass.prototype = Object.create(objectConstructor.prototype);
    var instance = new OtherClass();
    instance._initPrivates(aPrivateFunctions);
    
    // delete the initiation functions
    delete instance._initPrivates;
    
    return instance;
    */

    // THIRD TRY, WORKS WITH PROTOYPES AND ARGUMENTS
    var instance = Object.create(objectConstructor.prototype);
    var otherstring = objectAsString.substring(0, objectAsString.length - 1)
             + ";"
             + "this.prototype=Object.create(objectConstructor.prototype);\n"
             + "this._privMems = {};\n"
             + "this._initPrivates = function(pf) {"
             + "  this._privMems = {};"
             + "  for (var i = 0, ii = pf.length; i < ii; i++)"
             + "  {"
             + "    var fn = pf[i].replace(/(function\\s+)/, '').replace('(', '');"
             + "    try { "
             + "      this._privMems[fn] = eval(fn);"
             + "    } catch (e) {"
             + "      if (e.name == 'ReferenceError') { continue; }"
             + "      else { throw e; }"
             + "    }"
             + "  }"
             + "}"
             + "\n\n}";
    eval("var OtherClass = "+otherstring);
    OtherClass.apply(instance, args);
    instance._initPrivates(aPrivateFunctions);

    // delete the initiation functions
    delete instance._initPrivates;

    return instance;
};

/**** USAGE (comment this line to view) ****

var Person = function() {
    //defaults
    var _age  =  0,
        _name = 'John Doe';
     
    var socialSecurity = '444 555 666';
    var bloodType      = 'O negative'
    //this is a global variable
    hatSize            = 'medium';
    var noValue;
     
    var aTest = function() {
      var nestedVar = 'nestedVar';
      var nestedFunction = function() {
        return 'nestedFunction';
      };
       
      alert('aTest');
    },
      anotherTest = function() {
        alert('anotherTest');
    };
     
    function test1() {
      alert('test1');
      var obj = {
        test3: 'test3',
      bla:   234
      };
       
      function nestedFc() {
        alert('I am nested!');
      }
    }
     
    function test2() {
      alert('test2');
    }
     
    function test3() {
      alert('test3');
      
      return {
        test3: 'test3',
        bla:   234
      };
    }
     
    this.initialize = function(name, age) {
      _name = _name || name;
      _age  = _age  || age;
    };
     
    if (arguments.length) this.initialize();
     
    //public properties. no accessors required
    this.phoneNumber = '555-224-5555';
    this.address     = '22 Acacia ave. London, England';
     
    //getters and setters
    this.getName     = function()      { return _name; };
    this.setName     = function (name) { _name = name; };
     
    //private functions
    function aFunction( arg1 ) {
      alert('I am a private function (ha!)');
    }
     
    //public methods
    this.addBirthday = function()      { _age++; };
    this.toString    = function()      { return 'My name is "+_name+" and I am "_age+" years old.'; };
};
 
//create an instance of a person
var rob = Reflection.createExposedInstance(Person); //new Person('Rob', 29); //still 29! (I wish!)
 
//document.write
rob._privMems['aFunction']();  //alerts "I am a private function (ha!)"

/* */

Suggestions are welcome.