I have a class 

```
function Node() {
    //implementation
}

```

and another class

```
function AttributionalNode() {
    this.prototype.setAttr = function (attr) {
        this.atText = attr;
    };
}

AttributionalNode.prototype = new Node();
AttributionalNode.prototype.constructor = AttributionalNode;

```

How to make class Node() so it can't be instantiated?
e.g when I try 

```
var node = new Node();

```

So it throws an Exception?