Jquery 如何将AJAX响应作为blob而不是字符串接收？

我使用以下AJAX调用从后端（正在运行Flask）获取Excel文件：

AJAX调用通过了，但是

done

方法中的

data

对象是一个字符串，而不是blob，这是我所期望的。对应于AJAX调用的flask路由如下所示：

@app.route("/export", methods = ['POST'])
def export():
    userid = session['userid']
    export_type = request.form['exportType']
    export = get_export(db, userid, export_type)
    output = io.BytesIO()
    writer = pd.ExcelWriter(output, engine='xlsxwriter')
    export.to_excel(writer)
    writer.save()
    output.seek(0)
    return send_file(output, attachment_filename = "Promotions_Export.xlsx", mimetype='application/vnd.ms-excel', as_attachment = True)

@app.route("/export", methods = ['POST'])
def export():
    userid = session['userid']
    export_type = request.form['exportType']
    export = get_export(db, userid, export_type)
    output = io.BytesIO()
    writer = pd.ExcelWriter(output, engine='xlsxwriter')
    export.to_excel(writer)
    writer.save()
    output.seek(0)
    return send_file(output, attachment_filename = "Promotions_Export.xlsx", mimetype='application/vnd.ms-excel', as_attachment = True)