Mutation Observer

mutationObserver.js

 var targetNode = document.querySelectorAll('.validation-message'), i;
            // Options for the observer (which mutations to observe)
  var config = { attributes: true, childList: true, subtree: true };

  var callback = function(mutationsList, observer) {
      for(var mutation of mutationsList) {
          if (mutation.type == 'childList') {
              //console.log('mutation.nextElementSibling', mutation.target.nextElementSibling.nextElementSibling);
              if(mutation.target.childNodes[0] && mutation.target.childNodes[0].length != 29){
                  if(mutation.target.nextElementSibling.className == "screen-reader"){
                      mutation.target.nextElementSibling.style.opacity = "0";
                  } else {
                      mutation.target.nextElementSibling.nextElementSibling.style.opacity = "0";
                  }
              } else {
                  if(mutation.target.nextElementSibling.className == "screen-reader"){
                      mutation.target.nextElementSibling.style.opacity = "1";
                  } else {
                      mutation.target.nextElementSibling.nextElementSibling.style.opacity = "1";
                  }
                  console.log('mutation False', mutation.target.childNodes[0].length);
              }
          }
      }
  };
  var observer = new MutationObserver(callback);

  for (i = 0; i < targetNode.length; ++i) {
      observer.observe(targetNode[i], config);
  }