It is not a rocket science to pass objects from child window (popup) to main window. The problem I encountered today was IE and passing complex objects. So it is just an IE issue as far as I know. The problem occurs when you pass some object (not a simple String or Number) to main window:

window.opener.takeAnObjectFromChild = { 
      title: "Should even be available when I close the child" 
};

and you then close the child window, next time the main window tries to access the passed object:

In javascript, if we copy objects or their properties, the reference still remains and by changing the new object the old one is changed, too. To clone or do a clean copy of an object I found a very useful solution by Jan Turoň on StackOverflow:

Object.prototype.clone = function() {
  if(this.cloneNode) return this.cloneNode(true);
  var copy = this instanceof Array ? \[\] : {};
  for(var attr in this) {
    if(typeof this\[attr\] == "function" || this\[attr\]==null || !this\[attr\].clone)
      copy\[attr\] = this\[attr\];
    else if(this\[attr\]==this) copy\[attr\] = copy;
    else copy\[attr\] = this\[attr\].clone();
  }
  return copy;
}

Date.prototype.clone = function() {
  var copy = new Date();
  copy.setTime(this.getTime());
  return copy;
}

Number.prototype.clone = 
Boolean.prototype.clone =
String.prototype.clone = function() {
  return this;
}

Next: clone your objects if you pass them from a popup.