Is there any way to copy a JavaScript function Scope to another function?

```
(function(v){
     var Ct=v.Ct=function(){
     }
     var a="asdf";

     Ct.prototype.fun=function(){
          console.log(a);    //prints 'asdf'
     }
})(window)

--------------------------------------------------

```

the above code cannot be changed:

how to rewrite Ct.prototype.fun to make it print 'asdfasdf'

the following example can not get "a"

```
Ct.prototype.fun=function(){
    console.log(a+a);   //It's not work
}

var o=new Ct();
o.fun();

```