JSFiddle - React, Tailwind, and code Playground

JavaScript

function xx(num){
    return num.toString().replace(/^(\d$)/,'0$1')
                       }

jourdhui=new Date();
jour=xx(jourdhui.getDate())
mois=xx(jourdhui.getMonth()+1)
an=xx(jourdhui.getFullYear())
alert(jour+'-'+mois+'-'+an)