How to fade in image when scroll to image and remain fade in until page is refresh

Question

I'm trying wow.js library for fade in animation when scroll to that div and remains fade in until page is refresh again but wow.js library is not working as expected it loads div before reaching to div

<div class="app wow fadeIn"  data-wow-delay="1.2s" style="visibility: visible; animation-delay: 1.2s; animation-name: fadeIn;">
         <div id="chartdiv"> </div>
    </div>
</div>