$filename = 'demo.xlsx';
$objWriter = \PHPExcel_IOFactory::createWriter($objectPHPExcel, 'Excel2007');
ob_start();
$objWriter->save("php://output");
$xlsData = ob_get_contents();
ob_end_clean();
return Api::success(['filename' => $filename, 'file' => "data:application/vnd.ms-excel;base64," . base64_encode($xlsData)]);

$('.download').click(function(){
    var url = "http://xxxx.com/group/bi/export";
    var params = {
      from_date: '2017-09-01',
      to_date: '2017-09-08',
      group_id: 1
    };
    $.ajax({
      type:'POST',
      url: url,
      data: params,
      beforeSend: function(request) {
        request.setRequestHeader("Authorization", "token信息，验证身份");
      },
      success: function(redata) {
        // 创建a标签，设置属性，并触发点击下载
        var $a = $("<a>");
        $a.attr("href", redata.data.file);
        $a.attr("download", redata.data.filename);
        $("body").append($a);
        $a[0].click();
        $a.remove();
      }
    });
});