let URL = this.dataURLtoBlob(res.data);
var reader = new FileReader();
  reader.readAsDataURL(URL);
  reader.onload = function (e) {
    // 兼容IE
    if (window.navigator.msSaveOrOpenBlob) {
      var bstr = atob(e.target.result.split(",")[1]);
      var n = bstr.length;
      var u8arr = new Uint8Array(n);
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n);
      }
      var blob = new Blob([u8arr]);
      window.navigator.msSaveOrOpenBlob(blob,‘采购单.pdf‘);
    } else {
      // 转换完成,创建一个a标签用于下载
      var a = document.createElement(‘a‘);
      a.download = ‘采购单.pdf‘;
      a.href = e.target.result;
      a.setAttribute("id", "export")
      document.getElementById("purchaseManage").append(a); // 修复firefox中无法触发click
      a.click();
      document.getElementById("export").remove();
  }
}