var url = '124.333.444.txt.pdf.xlxs'
var reg = /\.\w+$/;
var fileName = url.replace(reg, '');
console.log('fileName', fileName); // 124.333.444.txt.pdf
var url = '124.333.444.txt.pdf.xlxs'
const FileExt = url.replace(/.+\./, ""); // xlxs
const fileExtension = url.substring(url.lastIndexOf('.') + 1); // xlxs