Detect when iOS Safari landscape menu opens and closes

safari_lanscape_menu.js

/**
 * Credit to https://stackoverflow.com/a/29696509
 */
const isMobileSafari = () => {
  const ua = window.navigator.userAgent;
  const iOS = ua.match(/iPad/i) || ua.match(/iPhone/i);
  const webkit = ua.match(/WebKit/i);
  return iOS && webkit && !ua.match(/CriOS/i);
};

/**
 * Call this from your onresize handler and handle your update(s)
 */
const isSafariLandscapeMenuOpen = () => {
  const innerWidth = window.innerWidth,
        innerHeight = window.innerHeight,
        isLandscape = innerHeight > innerWidth,
        bodyOffsetHeight = document.body.offsetHeight;

  return isLandscape && isMobileSafari() && (bodyOffsetHeight > innerHeight);
};