常见Ajax下载文件方式以及报错解决办法

// 点击下载按钮时触发
$("#download-btn").click(function() {
  // 发送 AJAX 请求获取字节数组
   $.ajax({
            url: url,
            type: "GET",
            xhrFields: { responseType: "blob" },
            success: function (response, status) {
            
                var blob = new Blob([response], { type: "application/pdf" });// 此转换为xhrFields: { responseType: "arraybuffer" },
                
                var link = document.createElement("a");
                link.href = window.URL.createObjectURL(response);
                link.download = "example.pdf";
                document.body.appendChild(link);
                link.click();
            },
            error: function (xhr, status, error) {
                console.log("Error:", error);
            }
        });
});

 Response.Headers.Add("fileName", fileExtensionName);
 Response.Buffer = false;
 var bytes = new byte[renderingResult.DocumentBytes.Length];
 renderingResult.DocumentBytes.CopyTo(bytes, 0);
//return File(bytes, System.Net.Mime.MediaTypeNames.Application.Octet, fileExtensionName);
 return File(renderingResult.DocumentBytes, renderingResult.MimeType, fileExtensionName);nsionName);

      var req = new XMLHttpRequest();
        req.open("GET", url, true);
        req.responseType = "blob";
        req.onloadstart = function (e) {
            console.log('e.onloadstartloaded', e.loaded)
        }
        req.onprogress = function (e) {
            var pb = $("#progressBar").data("kendoProgressBar");
            var prog = $("#progressBarLoad");

            console.log('e.loaded', e.loaded)
            console.log('e.total', e.total)
            //if (e.lengthComputable) {
            //    pb.value(Math.round(e.loaded * 100 / e.total));
            //    prog.text('done');
            //} else {
            //    prog.text(loaded);
            //}
 
        } //下载监听
        req.onload = function (oEvent) {
            if (req.status === 200) {
                var blob = req.response;
                var blobData = new Blob([req.response]);
                var fileName = req.getResponseHeader("fileName")
                if (fileName) {
                    var link = document.createElement('a');
                    link.href = window.URL.createObjectURL(req.response);
                    link.download = fileName;
                    link.click();
                    link.remove();
                    window.URL.revokeObjectURL(link.href);
                } else {
                    location.reload();
                }
                //kendo.ui.progress(ele, false);
            } else {
                console.log('error')
                kendo.ui.progress(ele, false);
            }
        };
        req.onloadend = function (e) {
            //$("#progressBar").hide();
            $("#progressBarLoad").text('done');
        }
        req.send();

Response.Buffer = false;

   var bytes = new byte[renderingResult.DocumentBytes.Length];
            renderingResult.DocumentBytes.CopyTo(bytes, 0);

            Response.Clear();
            Response.ContentType = renderingResult.MimeType;
            Response.Cache.SetCacheability(HttpCacheability.Private);
            Response.Expires = -1;
            Response.Buffer = true;
            Response.BinaryWrite(renderingResult.DocumentBytes);
            Response.Flush();
            Response.End();
            return string.Empty; ;
            //return File(bytes, renderingResult.MimeType);