KeyboardEvent.which value for tab key\nconst ARROW_UP_KEYCODE = 38 // KeyboardEvent.which value for up arrow key\nconst ARROW_DOWN_KEYCODE = 40 // KeyboardEvent.which value for down arrow key\nconst RIGHT_MOUSE_BUTTON_WHICH = 3 // MouseEvent.which value for the right button (assuming a right-handed mouse)\nconst REGEXP_KEYDOWN = new RegExp(`${ARROW_UP_KEYCODE}|${ARROW_DOWN_KEYCODE}|${ESCAPE_KEYCODE}`)\n\nconst CLASS_NAME_DISABLED = 'disabled'\nconst CLASS_NAME_SHOW = 'show'\nconst CLASS_NAME_DROPUP...