This returns a collection of JSS classes. These are associative arrays that contain other associative arrays. They don't inherit properties and methods from the Array object class and are particularly difficult to operate on.
If you are working with JSS driven style sheets, for a start your project is not portable across browser. It will only work on Netscape. Secondly, you are using deprecated functionality. This will lead to your project code breaking at some time in the future when JSS support is no longer available.