Javascript代码可以很好地下载图像，但不能下载PDF文件

function downloadPDF(url) {
  var link = document.createElement('a');
  link.href = url;
  link.download = 'file.pdf';
  link.click();
}

function downloadPDF(url) {
  var xhr = new XMLHttpRequest();
  xhr.open('GET', url, true);
  xhr.responseType = 'blob';
  xhr.onload = function() {
    if (xhr.status === 200) {
      var blob = xhr.response;
      var link = document.createElement('a');
      link.href = window.URL.createObjectURL(blob);
      link.download = 'file.pdf';
      link.click();
    }
  };
  xhr.send();
}