It's fun! Maybe not as fun as drinking kool-aid but compared to the complexivity of other languages, we have a champ.
You want to add an oldValue property to the string
String.prototype.oldValue = “the old value”;
Beware! All the new String objects and the one already declared will have a property with the value “the old value” inside. I can't think of a particular reason why one would do this. If you have one, please comment.