JavaScript property inheritance

I'm trying to have a generic 'List' class, which will have:

• Property: Items - which would be an array of 'what-ever'
• Method: Add() - which would be abstract and implemented by the specific 'List' object
• Method: Count() - which returns the number of 'items'

And then create sub-classes which will inherit from 'List':

// Class 'List'
function List(){
    this.Items = new Array();
    this.Add = function(){ alert('please implement in object') }
}

// Class CDList - which inherits from 'List'
function CDList(){
    this.Add = function(Artist){
        this.Items.push(Artist)
    }
}
CDList.prototype = new List();
CDList.prototype.constructor = CDList;

// Create a new CDList object
var myDiscs = new CDList();
myDiscs.Add('Jackson');
myDiscs.Count()  <-- this should be 1


// Create a second CDList object
var myDiscs2 = new CDList();
myDiscs2.Add('Walt');
myDiscs2.Add('Disney');
myDiscs2.Count()  <-- this should be 2

...but this seems to create a shared 'Items' list for all 'CDList' instances. I need to somehow have a new inherited instance of the 'Items' list for each 'CDList' instance.

How can I do this?

*I'm using in this example the 'Items' list as an example. I'd like to be able to have in my sub-classes a new instance for any type of inherited property - not necessarily an Array object.