$.ajax({
   type: 'post',
   url: "",
   xhrFields: { responseType: "blob" },  // 主要是这一句
   data: {},
   success: function(data) {
     that.download(data,'自己起的名字.xlsx')
   }
 })
},
download(data, fileName) {
 if (!data) {
   return
 }
 let url = window.URL.createObjectURL(new Blob([data]))
 let link = document.createElement('a');
 link.style.display = 'none';
 link.href = url;
 link.setAttribute('download', fileName);
 document.body.appendChild(link);
 link.click();
}