JSFiddle - React, Tailwind, and code Playground

HTML

<div class="out">
    <div class="inner"></div>
</div>
<div class="this-div-kills-browsers">
</div>

CSS

.out {
    width: 100%;
    height: 800px;
    background: url(https://placekitten.com/1200/800) no-repeat;
}
.this-div-kills-browsers {
    height: 1000px;
}

JavaScript

var hideThatKitty = $('.out').innerHeight();

$(window).on('scroll', function () {
     hideThatKitty = hideThatKitty/$('.this-div-kills-browsers').offset().top    
    $('.inner').css('background', rgba(255, 255, 255, \''0'+hideThatKitty\'));
});