standardnotes-app/app/assets/javascripts/Hooks/useBeforeUnload.tsx

import { useEffect } from '@node_modules/preact/hooks'

export const useBeforeUnload = (): void => {
  useEffect(() => {
    window.onbeforeunload = () => true

    return () => {
      window.onbeforeunload = null
    }
  }, [])
}