javascript convertir une date au format aaaa-mm-jj
// `date` is a `Date` object
const formatYmd = date => date.toISOString().slice(0, 10);
// Example
formatYmd(new Date()); // 2020-05-06
javascript format de date aaaa-mm-jj
let today = new Date()
today.toISOString().split('T')[0]
javascript format de date mm/jj/aaaa
var date_format = new Date();
document.write(innerHTML = date_format.getMonth()+'/'+ date_format.getDate()+'/'+date_format.getFullYear());