In below code i am creating XLS file using lightning javascript controller but it is ending up with creating an xls file how i can create XLSX file?? in the same way if i create xlsx file, file is not opening..


var hiddenElement = document.createElement('a');
        hiddenElement.href = 'data:application/vnd.ms-excel;charset=utf-8' + ',' + encodeURIComponent(csv);
        hiddenElement.download = 'Report.xls'; 
        hiddenElement.style="border: 1.5pt"; 
        document.body.appendChild(hiddenElement); // Required for FireFox browser
        hiddenElement.click();