const root = document.body;

const wrapper = document.createElement("div");
wrapper.id = "wrapper";
wrapper.innerHTML = `
  <ul id="list">
    <li>Alpha</li>
    <li id="middle">Beta</li>
    <li>Gamma</li>
  </ul>
`;
root.appendChild(wrapper);

const middle = document.getElementById("middle");

console.log("parentElement:", middle.parentElement.id);
console.log("previousElementSibling:", middle.previousElementSibling.textContent);
console.log("nextElementSibling:", middle.nextElementSibling.textContent);
console.log("firstElementChild of list:", middle.parentElement.firstElementChild.textContent);
console.log("lastElementChild of list:", middle.parentElement.lastElementChild.textContent);
console.log("children count:", middle.parentElement.children.length);