Up: Select the previous visible tree item.
Down: Select next visible tree item.
Left: Collapse the currently selected parent node if it is expanded. Move to the previous parent node (if possible) when the current parent node is collapsed.
Right: Expand the currently selected parent node and move to the first child list item.
Enter: Toggle the expanded or collapsed state of the selected parent node.
Home: Select the root parent node of the tree.
End: Select the last visible node of the tree.
Add role="tree" on the wrapper
Add role="treeitem" on the individual items
Indicate state with aria-hidden and aria-expanded attributes on focused and expanded items