<html>
  <head>
    <script src="assets/sentineljs/sentinel.js"></script>
    <style>
      .my-div-1 {
        display: none;
        height: 20px;
        border: 1px solid red;
        margin: 5px 0;
      }

      .my-div-2 {
        height: 20px;
        border: 1px solid blue;
        margin: 5px 0;
      } 
    </style>
    <script>
      // use the `sentinel` global object
      sentinel.on('.my-div-1', function(el) {
        el.innerHTML = 'my-div-1';
      });

      sentinel.on('.my-div-2', funct