Use new Date() to generate a new Date object containing the current date and time.

var today = new Date();
var dd = String(today.getDate()).padStart(2, '0');
var mm = String(today.getMonth() + 1).padStart(2, '0'); //January is 0!
var yyyy = today.getFullYear();

today = mm + '/' + dd + '/' + yyyy;
document.write(today);

This will give you today's date in the format of mm/dd/yyyy.

Simply change today = mm +'/'+ dd +'/'+ yyyy; to whatever format you wish.