JSFiddle - React, Tailwind, and code Playground

by Kocsten

HTML

<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
<div id="sartumolsa_surenta">
  <a href="http://zornet.ru/"><img src="https://image.prntscr.com/image/jPNVXU2OQrajpaXFh9W7iQ.png" alt="вызвать мастера"></a>
</div>

CSS

#sartumolsa_surenta {
  position: fixed;
  right: 0px;
  bottom: 0px;
  display: none;
}

#sartumolsa_surenta img {
  opacity: 0.3;
  cursor: pointer;
}

#sartumolsa_surenta img:hover {
  opacity: 1;
}

JavaScript

jQuery(function(f) {
  var element = f('#sartumolsa_surenta');
  f(window).scroll(function() {
    element['fade' + (f(this).scrollTop() > 100 ? 'In' : 'Out')](500);
  });
});