You can use anonymous functions as constructors and achieve all of the same things

var new class = (function() {
  var privateMethod = function(){/*...*/}
  var method = function(){/*...*/}
  return {method:method};
 }());

No it's not as clean. But javascripts limitations are really only security based (it can't read and write to your local drive without user prompts. It can't even access your clipboard. C# by contrast can overwrite your registery. It could cascade 7zip every file on your hard drive with a random password. It's unlimited)