useWindowSize.js

import { useState, useEffect } from "react";

export default function useWindowSize() {
  const [{width, height}, setSize] = useState({ window.innerWidth, window.innerHeight });

  useEffect(() => {
    const handleResize = () => setSize({ window.innerWidth, window.innerHeight });
    window.addEventListener("resize", handleResize);
    return () => {
      window.removeEventListener("resize", handleResize);
    };
  }, [setSize]);

  return {width, height}; // or: return [width, height] 
}