<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
  </head>

  <body>
    <ul id="myList">
      <li id="item1">项目 1</li>
      <li id="item3">项目 3</li>
      <li id="item2">项目 2</li>
      <li id="item4">项目 4</li>
    </ul>

    <script>
      function sortAndReturnTextContent() {
        const items = document.getElementById("myList").children;
        // 在此补全代码
        const myList = document.getElementById("myList");
        for (let i = 1; i <= items.length; i++) {
          let node = document.getElementById(`item${i}`);
          myList.appendChild(node);
        }
      }
      sortAndReturnTextContent();
    </script>
  </body>
</html>