import React, { useState, useEffect } from 'react'; const UseEffectCleanup = () => { const [width, setWidth] = useState(window.innerWidth); const checkSize = () => { setWidth(window.innerWidth) } useEffect(() => { window.addEventListener('resize', checkSize) return () => { window.removeEventListener('resize', checkSize) } }, [width]); return ( <> <h1>Window Size</h1> <h2>{`${width}px`}</h2> </> ); } export default UseEffectCleanup;