Marks the beginning of an undo group, which allows a script to logically group all of its actions as a single undoable action (for use with the Edit > Undo/Redo menu items). Use the endUndoGroup() method to mark the end of the group. ()
beginUndoGroup() and endUndoGroup() pairs can be nested. Groups within groups become part of the larger group, and will undo correctly. In this case, the names of inner groups are ignored.
undoSt r ing The text that will appear for the Undo command in the Edit menu (that is, Undo