最近やっているClassの書き方です。

gistfile1.txt

var MyClass = (function(){

	function MyClass(){}
	
	MyClass.prototype.doIt = function(a, b){
		console.log('doIt');
		this._doProtected();
		privates.doSecret.call(this, a, b);
	};
		
	MyClass.prototype._doProtected = function(){
		//protected
		console.log('protected');
	}

	var privates ={
		
		doSecret: function(){
			//private
			console.log('private');
		}
		
	};
	
	return MyClass;

})();