Как отследить событие position: sticky

$('.header h1').Stickyfill();

.header h1 { 
  color: #fff; 
  font-size: 26px; 
  background-color: #ccc; 
  text-align: center; 
  margin: 0; 
  position: sticky; 
  position: -webkit-sticky; 
  position: -moz-sticky; 
  position: -ms-sticky; 
  position: -o-sticky; 
  top: 0; 
} 
 
.content { 
  background-color: #333; 
} 
 
.content span { 
  display: block; 
  color: #fff; 
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 
<script src="https://rawgit.com/wilddeer/stickyfill/master/dist/stickyfill.js"></script> 
<div class="header"> 
  <h1>Sticky block</h1> 
</div> 
<div class="content"> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
  <span>Content text Content text Content text</span> 
</div>