The element with role button has aria-haspopup set to either menu or true.
When the menu is displayed, the element with role button has aria-expanded set to true. When the menu is hidden, it is recommended that aria-expanded is not present. If aria-expanded is specified when the menu is hidden, it is set to false.
Keyboard interaction:
With focus on the button:
Enter: opens the menu and places focus on the first menu item.
Space: Opens the menu and places focus on the first menu item.
A parent menuitem has aria-haspopup set to either menu or true.
A parent menuitem has aria-expanded set to false when its child menu is not visible and set to true when the child menu is visible.
An element with role menu either has:
1)aria-labelledby set to a value that refers to the menuitem or button that controls its display.
2)A label provided by aria-label.
Keyboard:
down arrow: When focus is in a menu, moves focus to the next item, optionally wrapping from the last to the first.
up arrow: When focus is in a menu, moves focus to the previous item, optionally wrapping from the first to the last.
right arrow: When focus is in a menubar, moves focus to the next item, optionally wrapping from the last to the first.
left arrow: When focus is in a menubar, moves focus to the previous item, optionally wrapping from the first to the last.
Keyboard interaction:
Keyboard: