removeClass(classNames, el) {
    if (!classNames) {
      el.removeAttribute("class");
      return;
    }
    if (!Array.isArray(classNames)) classNames = [classNames];
    if (el) el.classList.remove(...classNames);
  }
Remove All, 1 or more class names from an element
@param {undefined|null|""|string|string[]} classNames Single or array of classnames. If undefined, "" or null, remove all classes
@param {HTMLElement} el HTML Element to add class(es) to