let element = document.querySelector('.element')

let top = sessionStorage.getItem('element-scroll')

if (top !== null) {
  element.scrollTop = parseInt(top, 10)
}

window.addEventListener('pagehide', () => {
  sessionStorage.setItem('element-scroll', element.scrollTop)
})

Use pagehide rather than beforeunload — beforeunload is unreliable on mobile and makes the page ineligible for the back/forward cache.

If you just want the browser to restore the whole page’s scroll position, you don’t need any of this — that’s what history.scrollRestoration controls, and it’s on by default.