useTimeout hook

useTimeout.ts

import React, { useEffect, useRef } from 'react';

const useTimeout = (callback: () => void, delay: number | null) => {
  const savedCallback = useRef(callback);

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

  useEffect(() => {
    function tick() {
      savedCallback.current();
    }

    if (delay !== null) {
      const id = setTimeout(tick, delay);
      return () => clearTimeout(id);
    }
  }, [delay]);
};

export default useTimeout;

Line 7 and 12 generates a typescript error:
Type '() => void' is not assignable to type 'undefined'.

Line 7 and 12 generates a typescript error:
Type '() => void' is not assignable to type 'undefined'.

Thanks for pointing that out. I updated the gist to include the callback into the useRef call so that Typescript understands it will never be undefined.