The JQuery API has been changed. The API changes in jQuery 1.8.0 deal primarily with animations and general cleanup.
.addBack() in: Traversing
Add the previous set of elements on the stack to the current set, optionally filtered by a selector.
Utility method to filter and/or chain Deferreds.
Select the element at index n within the matched set.
Parses a string into an array of DOM nodes.