async download()}{
  await downloadFile().then(res => {
    //此处res为返回的base64编码
    let bstr = atob(res)
    let n = bstr.length
    let u8arr = new Unit8Array(n)
    while(n--){
      u8arr[n] = bstr.charCodeAt(n)
    }
    if(window.navigator && window.navigator.msSaveOrOpenBlob){
      window.navigator.msSaveOrOpenBlob(new Blob([u8arr]),'我是文件名')
    }else{
      const link = document.createElement('a')
      link.href = URL.createObjectURL(new Blob([u8arr]))
      link.download = '我是文件名'
      link.click()
      URL.revokeObjectURL(link.href)
    }
  })
}