有没有办法在JavaScript中检测下载的开始？

const startTime = new Date().getTime();

fetch('https://example.com/file')
  .then(response => {
    const endTime = new Date().getTime();
    const downloadTime = endTime - startTime;
    console.log('下载开始');
    console.log(`下载时间：${downloadTime} 毫秒`);
  })
  .catch(error => console.error('下载出错', error));

<a href="https://example.com/file" download id="download-link">下载文件</a><script>
  const link = document.getElementById('download-link');
  let startTime;

  link.addEventListener('click', () => {
    startTime = new Date().getTime();
    console.log('下载开始');
  });

  window.addEventListener('focus', () => {
    if (startTime) {
      const endTime = new Date().getTime();
      const downloadTime = endTime - startTime;
      console.log(`下载时间：${downloadTime} 毫秒`);
      startTime = null;
    }
  });
</script>