The Selection.extend() method moves the focus of the selection to a specified point. The anchor of the selection does not move. The selection will be from the anchor to the new focus, regardless of direction.
extend(node)
extend(node, offset)nodeThe node within which the focus will be moved.
offset OptionalThe offset position within node where the focus will be moved to. If not specified, the default value 0 is used.
None (undefined).
Selection, the interface it belongs to.