Adaugă "de" la sfârșitul unui număr dacă este cazul.

dozens.js

var date = new Date('November 09 2019');
var current_day = date.getDate();
var base_forms = 5;
var forms = base_forms + current_day * 12;
var dozens = forms / 100;
var dozens = dozens.toString();
var dozens = dozens.split(".")[1];
var dozens = parseInt(dozens, 10);
if (dozens > 19) {
  var forms = forms.toString() + ' de';
} else {
  var forms = forms;
}