Composing Behavior with React hooks - useInterval

useInterval.ts

import { useRef, useEffect } from "react";

export default function useInterval(callback, delay) {
  const savedCallback = useRef(null);

  useEffect(() => {
    savedCallback.current = callback;
  });

  useEffect(
    () => {
      function handler() {
        savedCallback.current();
      }
      let intervalId = null;
      if (delay > 0) {
        intervalId = setInterval(handler, delay);
      }
      return () => {
        if (intervalId) {
          clearInterval(intervalId);
          intervalId = null;
        }
      };
    },
    [delay]
  );
}