js发送post请求，实现下载文件

由于业务需求要下载文件的功能：
  <!DOCTYPE html>

        <html>

        <head>

            <meta charset="utf-8">

            <meta name="renderer" content="webkit|ie-comp|ie-stand">

            <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">

            <meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no"/>

            <meta http-equiv="Cache-Control" content="no-siteapp"/>

            </head>

            <body>

            <input type="button" id="clickme" value="clickme" />

            </body>

             <script type="text/javascript">

             function postExcelFile(params, url) { //params是post请求需要的参数，url是请求url地址

                var form = document.createElement("form");

                form.style.display = 'none';

                form.action = url;

                form.method = "post";

                document.body.appendChild(form);

                for(var key in params){

                  var input = document.createElement("input");

                  input.type = "hidden";

                  input.name = key;

                  input.value = params[key];

                  form.appendChild(input);

                }

                form.submit();

                form.remove();

              }

              //点击导出按钮导出excel表格

              clickme.onclick = function() {

                var params = {};

                //params.queryDateEnd='20180709';

                //params.queryDate='20180709';

                //params.productId=0;

                // params.chnMerchant='咪咕视讯,咪咕+,内部导流';

                //params.chnAttr='咪咕视讯自有渠道,咪咕互娱';

//params.chnID='101700010000009,308500040040028,101800000030119,10290001916,101400030060133';

                //postExcelFile(params, "http://localhost:8082/kpi/chnOperate/export");

                params.queryDate='2018-08-16';

                params.productId=0;

                params.channel1Id='12924,12925,12926';

                params.channel2Id='332584,12927,333950,314216';

                //params.channel3Id='332585,12938,333951';

                //params.channel4Id='335273,332081,336699';

                //params.chnID='201600010000758,202400000000006';

                  postExcelFile(params, "http://wxs.ngrok.xiaomiqiu.cn/kpi/chnOperate/realTime/daily/list/export");

              }

             </script>

            </html>