Function useStateList

src/useStateList.ts:17–77

(stateSet: T[] = [])

}

export default function useStateList<T>(stateSet: T[] = []): UseStateListReturn<T> {
  const isMounted = useMountedState();
  const update = useUpdate();
  const index = useRef(0);

  // If new state list is shorter that before - switch to the last element
  useUpdateEffect(() => {
    if (stateSet.length <= index.current) {
      index.current = stateSet.length - 1;
      update();
    }
  }, [stateSet.length]);

  const actions = useMemo(
    () => ({
      next: () => actions.setStateAt(index.current + 1),
      prev: () => actions.setStateAt(index.current - 1),
      setStateAt: (newIndex: number) => {
        // do nothing on unmounted component
        if (!isMounted()) return;

        // do nothing on empty states list
        if (!stateSet.length) return;

        // in case new index is equal current - do nothing
        if (newIndex === index.current) return;

        // it gives the ability to travel through the left and right borders.
        // 4ex: if list contains 5 elements, attempt to set index 9 will bring use to 5th element
        // in case of negative index it will start counting from the right, so -17 will bring us to 4th element
        index.current =
          newIndex >= 0
            ? newIndex % stateSet.length
            : stateSet.length + (newIndex % stateSet.length);
        update();
      },
      setState: (state: T) => {
        // do nothing on unmounted component
        if (!isMounted()) return;

        const newIndex = stateSet.length ? stateSet.indexOf(state) : -1;

        if (newIndex === -1) {
          throw new Error(`State '${state}' is not a valid state (does not exist in state list)`);
        }

        index.current = newIndex;
        update();
      },
    }),
    [stateSet]
  );

  return {
    state: stateSet[index.current],
    currentIndex: index.current,
    isFirst: index.current === 0,
    isLast: index.current === stateSet.length - 1,