Selection.getRangeAt()

The getRangeAt() method of the Selection interface returns a range object representing a currently selected range.

If the endpoints of the selected range are within a shadow tree then JavaScript does not have visibility of the shadow nodes, and the method should re-scope the range to include the host element that contains the end point. In practice most browsers do not yet implement this behavior, and the returned range is unpredictable.

Note: When selecting within nodes that might contain a shadow root, you can use Selection.getComposedRanges() (if supported) to get a selection range inside a shadow tree, or to reliably re-scope the selection to the host node.