// 创建一个简单的 XML 文档
var xmlData = <bookstore>
                <book>
                  <title>Introduction to JavaScript</title>
                  <author>John Doe</author>
                </book>
                <book>
                  <title>Web Development Basics</title>
                  <author>Jane Smith</author>
                </book>
              </bookstore>;

// 访问 XML 数据
var firstBookTitle = xmlData.book[0].title;
var secondAuthor = xmlData.book[1].author;

// 修改 XML 数据
xmlData.book[0].title = "JavaScript Fundamentals";

// 添加新元素
xmlData.book[0].appendChild(<publishedYear>2023</publishedYear>);

// 输出修改后的 XML 数据
console.log(xmlData);