利用html a標籤下載

（1）鏈接的 onclick 事件被先執行，其次是 href 屬性下的動作（頁面跳轉，或 javascript 僞鏈接）

（2）假設鏈接中同時存在 href 與 onclick，如果想讓 href 屬性下的動作不執行，onclick 必須得到一個 false 的返回值。

（3）如果頁面過長有滾動條，且希望通過鏈接的 onclick 事件執行操作。應將它的 href 屬性設爲 javascript:void(0);，而不要是 #，這可以防止不必要的頁面跳動；

（4）如果在鏈接的 href 屬性中調用一個有返回值的函數，當前頁面的內容將被此函數的返回值代替；

 

<a href="javascript:void(0);" onclick="download()" style="color: blue" download>Download</a>

function download() {
    let url = window.location.protocol + '//' + window.location.host + '/download';
    url = url + '?userAge=' + $("#userAge").val();
    url = url + '&userId='+$("#userId").val();
    url = url + '&userName='+encodeURIComponent(encodeURIComponent($("#userName").val()));
    window.location.href = url;
    return false;
}

@xxx.route('/download', methods=['GET'])
@login_required
def download():
    user_id = request.args.get('userId')
    user_age = request.args.get('userAge')
    user_name = urlparse.unquote(request.args.get('userName'))
    logger.info('userId: {0}, userAge: {1}, userName: {2}'.format(str(user_id), str(user_age), str(user_name)))
    connection = engine.raw_connection()
    df = pd.DataFrame()
    try:
        cursor = connection.cursor()
        cursor.callproc("xxx_xxxx", [user_name, user_age])
        sql = "select * from  xxx_xxx where userid=:user_id "
        df = pd.read_sql_query(sql, engine, params=[user_id])
        cursor.close()
        connection.commit()
    except Exception as e:
        logger.error('Get data error:' + str(e.message))
        logger.error(traceback.format_exc())
    finally:
        connection.close()

    output = BytesIO()
    writer = pd.ExcelWriter(output)
    df.to_excel(writer, index=False, sheet_name='Sheet')
    workbook = writer.book
    header_fmt = workbook.add_format({
        'font_size': 14,
        'bold': True,
        'fg_color': '#D7E4BC',
        'border': 1})
    sheet_table = writer.sheets['Sheet']
    for col_num, value in enumerate(df.columns.values):
        sheet_table.write(0, col_num, value, header_fmt)
    sheet_table.set_column('A:A', 30)
    sheet_table.set_column('B:B', 10)
    sheet_table.set_column('C:C', 30)
    sheet_table.set_column('D:I', 15)
    sheet_table.set_column('J:K', 20)
    workbook.close()
    writer.close()
    output.seek(0)
    return send_file(output, attachment_filename="Excel_Name.xlsx", as_attachment=True)