React-Native, flatlist onViewableItemsChanged get Index of page

onViewableItemsChanged.ts

// Quicker bi-directional onViewableItemsChanged

const [activeIndex, setActiveIndex] = useState(0);

const onViewableItemsChanged = useRef(({ viewableItems, changed }) => {
  if (viewableItems?.length >= 2 && changed?.[0]?.isViewable) {
    setActiveIndex(changed?.[0].index);
  } else {
    if (viewableItems?.[0]) setActiveIndex(viewableItems[0].index);
  }
}).current;