code: function getPreviousSiblings(el) {
    var siblings = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : [];
    var previousSibling = el.previousSibling;
  
    if (!previousSibling) {
      return siblings;
    }
  
    siblings.push(previousSibling);
    return getPreviousSiblings(previousSibling, siblings);
  }
docs: recursive function to get previous sibling nodes of given element