Result of activateMenuItem: the item's value and, for checkable items, its new state.
Optional
New checked state for menuitemcheckbox/menuitemradio; undefined for plain items.
menuitemcheckbox
menuitemradio
undefined
data-hl-value, falling back to the item's trimmed text.
data-hl-value
Result of activateMenuItem: the item's value and, for checkable items, its new state.