Some top nav examples

Native Bootstrap 3.3.7

Tab between menu triggers, arrow down and up throught the menus with roving tabindex trapping arrow in submenu

Bootstrap 3.3.7 with focus event listeners on dropdown links (shows menu, changes state of aria-expanded)

Menu keys disabled - all is done with tab

Fully instrumented W3 example: tab to nav, left/right arrow keys to navigate nav items, enter or arrown to open submenu, right to open sub-submenus (see original)