AJAX页面下载进度

var xhr = new XMLHttpRequest();
xhr.open('GET', 'https://example.com/file.zip', true);
xhr.responseType = 'blob';
xhr.onprogress = function(e) {
  if (e.lengthComputable) {
    var percentComplete = (e.loaded / e.total) * 100;
    console.log(percentComplete.toFixed(2) + '% downloaded');
  }
};
xhr.onload = function() {
  if (this.status == 200) {
    console.log('File downloaded successfully');
  }
};
xhr.send();