leftZeros

var bonds = [];
var limit = 6;
var leftZeros = limit - bonds[i].idTitulo.length;
var idTituloCompleted = '';

console.log("n", bonds[i].idTitulo);
console.log("leftZeros", leftZeros);
while (leftZeros) {
  console.log("oi left zero", idTituloCompleted)
  idTituloCompleted += "0";
  leftZeros--;
}

if (!leftZeros) {
  var newId = idTituloCompleted + bonds[i].idTitulo;
  console.log(newId);
  bonds[i]['idTituloWithDigits'] =  Utils.formatWithDigits(newId);
}