function calculer(form) {

  montant_emprunte = form.montant.value.replace(/\,/g,'');
  montant_emprunte = montant_emprunte.replace(/ /g,'');
  
  taux_interet = form.taux.value.replace(/\,/g,'.');
  taux_interet = taux_interet.replace(/%/g,'');
  taux_interet = taux_interet / 100;
  
  int_mensuel = taux_interet / 12;
  
  nb_mois = form.periode.value * 12;
  
  if(isNaN(montant_emprunte) || isNaN(taux_interet) || isNaN(nb_mois) || montant_emprunte == "" || taux_interet == "" || nb_mois == "") {
    alert("One or more fields are incorrectly filled");
  } else {
    mensualite = (montant_emprunte * int_mensuel) / (1 - (1 / Math.pow((1+int_mensuel),nb_mois)));
    total = (nb_mois * mensualite) - montant_emprunte;
  
    alert("Monthly: " + mensualite);
    alert("Total of the interest: " + total);
  }
  
  return false;

}