前端下载的几种方式，

//把上一次创建的iframe删掉，不然随着下载次数的增多页面上会一堆的iframe
var haveIframe = $("iframe")
if(haveIframe){
    haveIframe.remove();
}
downloadFile(url);
function downloadFile(url) {   
   try{ 
        var elemIF = document.createElement("iframe");   
        elemIF.src = url+‘?pSize=1&pNum=1&flag=1&sts=Y‘;   
        elemIF.style.display = "none";   
        document.body.appendChild(elemIF);   
    }catch(e){ 
        zzrw.alert("下载异常！");
    }     
}

//同样道理，把上一次创建的form删掉，不然随着下载次数的增多页面上会一堆的form
var haveForm = $("#downloadfileform")
if(haveForm){
    $("#downloadfileform").remove();
}
var $eleForm = $("<form id=‘downloadfileform‘ method=‘get‘><input id=‘input_data‘ name=‘data‘ type=‘hidden‘>" +
        "<input id=‘pSize‘ name=‘pSize‘ value=‘"+obj.pSize+"‘ type=‘hidden‘>"+
        "<input id=‘pNum‘ name=‘pNum‘ value=‘"+obj.pNum+"‘ type=‘hidden‘>"+
        "<input id=‘flag‘ name=‘flag‘ value=‘"+obj.flag+"‘ type=‘hidden‘>"+
        "<input id=‘sts‘ name=‘sts‘ value=‘"+obj.sts+"‘ type=‘hidden‘>"+
        "</form>");
$eleForm.attr("action",url);

$(document.body).append($eleForm);
//提交表单，实现下载
$eleForm.submit();

 //导出事件
    exportData() {
      this._shopMonthexport(this.getParams())
        .then(res => {
          const blob = new Blob([res.data], {
            type: "application/vnd.ms-excel;charset=utf-8"
          });//这里是excel文件，可根据需求自行更改
          var contentDisposition = res.headers["content-disposition"];
          var patt = new RegExp("filename=([^;]+\\.[^\\.;]+);*");
          var result = patt.exec(contentDisposition);
          var fileName = result[1];
          if ("download" in document.createElement("a")) {
            // 非IE下载
            const elink = document.createElement("a");
            var reg = /^["](.*)["]$/g;
            elink.download = decodeURI(fileName.replace(reg, "$1")); //下载后文件名
            elink.style.display = "none";
            elink.href = URL.createObjectURL(blob);//创建下载的链接
            document.body.appendChild(elink);
            elink.click();//点击下载
            URL.revokeObjectURL(elink.href); //释放掉blob对象
            document.body.removeChild(elink);//下载完成移除元素
          } else {
            // IE10+下载
            navigator.msSaveBlob(blob, fileName);
          }
        })
        .catch(e => {
          console.log(e);
        });
    },