How can I access local scope dynamically in javascript?

If you want to use global functions and variable dynamically you can use:

window[functionName](window[varName]);

Is it possible to do the same thing for variables in the local scope?

This code works correctly but currently uses eval and I'm trying to think of how else to do it.

var test = function(){
    //this = window
    var a, b, c; //private variables

    var prop = function(name, def){
        //this = window
        eval(name+ ' = ' + (def.toSource() || undefined) + ';');    

        return function(value){
            //this = test object
            if ( !value) {
                return eval('(' + name + ')');
            }
            eval(name + ' = value;')
            return this;
        };

    };

    return {
        a:prop('a', 1),
        b:prop('b', 2),
        c:prop('c', 3),
        d:function(){
            //to show that they are accessible via to methods
            return [a,b,c];
        }
    };
}();

>>>test
Object
>>>test.prop
undefined
>>>test.a
function()
>>>test.a()
1 //returns the default
>>>test.a(123)
Object //returns the object
>>>test.a()
123 //returns the changed private variable
>>>test.d()
[123,2,3]