dmorenogogoleva

export function usePrevious<T> (value: T): T | undefined {
  const ref = useRef<T>()

  useEffect(() => {
    ref.current = value
  }, [value])

  return ref.current
}

dmorenogogoleva

export function groupBy(collection: any[], iteratee: string) {
  return collection.reduce((result, value) => {
    if (!value.hasOwnProperty(iteratee)) return result

    const key = value[iteratee]

    if (!result || !result[key]) {
      result[key] = [value]
      return result
    }

dmorenogogoleva

export function usePreviousPersistent<T extends unknown>(value: T) {
  const ref = useRef<{ value: T; prev: T | null }>({
    value,
    prev: null,
  });

  const currentValue = ref.current.value;

  if (!isEqual(value, currentValue)) {
    ref.current = {

dmorenogogoleva

describe('some text', () => {
    it('my test', () => {
      const res = 2 +2
      expect((res)).toBe(4)
    })
});