JSFiddle - React, Tailwind, and code Playground

HTML

<div>
  <div>
    <input id="apartment" type="text">
    <div class="custom-placeholder">Кв./офис</div>
  </div>
  <div>
    <input id="floor" type="text">
    <div class="custom-placeholder">Этаж</div>
  </div>
  <div>
    <input id="entrance" type="text">
    <div class="custom-placeholder">Подъезд</div>
  </div>
  <div>
    <input id="intercom" type="text">
    <div class="custom-placeholder">Код домофона</div>
  </div>
</div>

CSS

.completed {color: blue; font-weight:bold;}

JavaScript

$('#floor, #entrance, #apartment, #intercom').on('blur', function(e) {
  if ($(this).val()) {
    $(this).next('.custom-placeholder').toggleClass('completed', true);
    sessionStorage.setItem("PlaceholderCompleted", $(this).attr("id"));
  } else {
    $(this).next('.custom-placeholder').removeClass('completed');
  }
});
  
var PlaceholderCompletedId = sessionStorage.getItem("PlaceholderCompleted");
if (PlaceholderCompletedId) {
  $("#" + PlaceholderCompletedId).siblings(".custom-placeholder").toggleClass('completed', true);
  console.log(PlaceholderCompletedId);
}