如何用普通的javaScript替换.prevAll()和.addBack()

function prevAll(element) {
  var siblings = Array.from(element.parentNode.children);
  var index = siblings.indexOf(element);
  return siblings.slice(0, index);
}

// 示例用法
var targetElement = document.getElementById('target');
var prevSiblings = prevAll(targetElement);
console.log(prevSiblings);

function addBack(elements, prevElements) {
  return elements.concat(prevElements);
}

// 示例用法
var elements = document.querySelectorAll('.element');
var prevElements = prevAll(elements[0]);
var allElements = addBack(elements, prevElements);
console.log(allElements);