Duplicate a javascript prototype instance?

I'm given an instance "aNode" of a prototype called "Node". Following this discussion (http://stackoverflow.com/questions/728360/copying-an-object-in-javascript), I attempt to:

var newNode = clone(aNode);
 

The clone function goes like:

function clone(obj) {
     if (null == obj || "object" != typeof obj) return obj;
     var copy = obj.constructor();
     for (var attr in obj) {
         if (obj.hasOwnProperty(attr)) copy[attr] = obj[attr];
     }
     return copy;
 }
 

Despite obj.consturctor() properly refers to aNode's constructor, copy is "underfined". Can't find why :(

Is this method wrong, or am I missing something :) ?

Thanks,
J.

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