[Javascript] accessing nested functions

[Pedro Mpa]

I'm having some trouble accessing nested functions, like in the following
example, how can I access function c ?

function a(){
	this.vara = "";

	this.b = function(){
		this.varb = "";

		this.c = function(){
			this.varc = "";
			alert('something');
		}
	}
}

Tried using:

test = new a();
test.b.c();

> test.b.c() Is not a function.

Is there a limit for nesting functions in JS ?

Thanks in advance.
Pedro.