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.

Alla känner nog till stackoverflow.com. Det finns även sådant för enbart Sharepoint Overflow. Värt att testa.