Fix for page scrolling issue on iOS on input focus in fixed element.

iOS-scroll-fix.js

open() {
  const offset = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop;
  document.body.style.top = (offset * -1) + 'px';
  document.body.classList.add('iOS-scroll-fix');
}

close() {
  const offset = parseInt(document.body.style.top, 10);
  document.body.classList.remove('iOS-scroll-fix');
  document.body.style.top = 0;
  window.scrollY = (offset * -1);
  document.documentElement.scrollTop = (offset * -1);
  document.body.scrollTop = (offset * -1);
}

.iOS-scroll-fix {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
}