如何从JavaScript网页下载完整的html？

function downloadHTML(url, filename) {
  var xhr = new XMLHttpRequest();
  xhr.open('GET', url, true);
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      var htmlContent = xhr.responseText;
      var a = document.createElement('a');
      a.href = 'data:text/html;charset=utf-8,' + encodeURIComponent(htmlContent);
      a.download = filename + '.html';
      a.click();
    }
  };
  xhr.send();
}

// 调用示例
downloadHTML('https://example.com/page.html', 'downloaded_page');