JSFiddle - React, Tailwind, and code Playground

JavaScript

var str = "21/12/2012";


if(str.match(/^(\d\d)\/(\d\d)\/(\d{4})$/)) {
    document.write('la date trouvée est le jour: ', RegExp.$1, ', mois: ', RegExp.$2, ', année: ', RegExp.$3);    
} else {
  document.write('date pas trouvée');   
}