function init() {

const IEoverlay = document.getElementsByClassName('IEPopup-wrapper')[0];

var ua = window.navigator.userAgent;
var msie = ua.indexOf("MSIE ");
var trident = ua.indexOf('Trident/');

if (IEoverlay && (msie > 0 || trident > 0)) {
    // IE
    IEoverlay.classList.add('active');

    const h2 = document.getElementsByClassName('IEPopup-window__headline')[0];
    const p = document.getElementsByClassName('IEPopup-window__text')[0];

    h2.innerHTML = TYPO3.lang['headline'];
    p.innerHTML = TYPO3.lang['text'];

    const x = document.getElementsByClassName('IEPopup-window__closebutton')[0];
    x.addEventListener('click', function () { IEoverlay.classList.remove('active') });
    }
}

init();