JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap-theme.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<div class="progress">
  <div class="progress-bar" role="progressbar" aria-valuenow="60" aria-valuemin="0" aria-valuemax="100" style="width:0%;">
    <span class="sr-only">60% Complete</span>
  </div>
</div>
<label id="lblIdade">0</label>
<button type="button" onclick="changeProgress()">Alterar</button>

JavaScript

function idade(d1, d2) {
  d2 = d2 || new Date();
  var diff = d2.getTime() - d1.getTime();
  return Math.floor(diff / (1000 * 60 * 60 * 24 * 365.25));
}

function changeProgress() {
  var value = idade(new Date(1988, 09, 3));
  $("#lblIdade").text(value);
  $(".progress .progress-bar").css('width', value);
}