Emulate clone constructor in js

clone.js

function CloneObject(obj)
{
  if (obj === null)
    return obj;
  if (typeof obj !== "object")
    return obj;

  var copy = obj.constructor();
  for (var attr in obj)
    if (obj.hasOwnProperty(attr))
      copy[attr] = arguments.callee(obj[attr]);
  return copy;
}