set focus to an iframe after loads its content

iframe-content.css

// hack to enable touch after focus on the iframe
html,
body {
  touch-action: auto;
}

iframe-set-focus.js

var iframe = window.document.querySelector('iframe');

// ...

function isSafari() {
  var ua = navigator.userAgent.toLowerCase();
  return ((ua.indexOf('safari') != -1) && (ua.indexOf('chrome') === -1));
}

function setIframeFocus() {
  iframe.focus();
  if(isSafari()) {
    window.setTimeout(function() {
      iframe.contentWindow.focus();
    }, 100)
  }
}

iframe.onload = setIframeFocus;

mobile-utils.js

// way to detect the old and newest iPad's
var isIPad = (window.navigator.userAgent.match(/(iPad)/) /* iOS pre 13 */ || 
  (window.navigator.platform === 'MacIntel' && window.navigator.maxTouchPoints > 1) /* iPad OS 13 */);

var isIOS = /iPad|iPhone|iPod/.test(navigator.platform)
|| (navigator.platform === 'MacIntel' && navigator.maxTouchPoints > 1);