后台下载，前端响应下载

            var xhr = new XMLHttpRequest();
            xhr.open("POST", "./technologyRuleHandler.ashx?Oper=download&path=" + $("#downloadText").val(), true);
            xhr.responseType = "blob";
            xhr.onload = function () {
                if (this.status == 200) {
                    var blob = this.response;
                    var reader = new FileReader();
                    reader.readAsDataURL(blob);
                    reader.onload = function (e) {
                        var a = document.createElement('a');
                        a.download = $("#downloadText").val();
                        a.href = e.target.result;
                        document.body.appendChild(a);
                        a.click();
                        document.body.removeChild(a);
                    }
                    $("#downloadModal").modal('hide');
                }
            };
            xhr.send();