JSFiddle - React, Tailwind, and code Playground

HTML

<div id="dos">
    holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa
     holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa
      holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa
       holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa
    </div>
    <div id="uno">
    holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
     holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
      holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
       holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
    holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
     holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
      holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
       holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
    holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
     holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
      holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
       holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
    holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa<br />
     holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa holaaaaaaaaa...

CSS

* {
            padding: 0;
            margin: 0;
            color: #fff;
        }
        div {
            position: relative;
            height: 1000px;
            overflow: hidden;
            padding: 50px;
        }
        #uno {
            background: url(http://www.fashiontargetsbreastcancer.org.au/Assets/images/panel_about_bg.jpg) 0 100% no-repeat;
        }
        #tres {
            background: url(parallax2.jpg) 0 0 no-repeat;
        }

JavaScript

$(document).ready(function(){
    var $w = $(window);
    var offset = $('#uno').offset().top;
    var $u = $('#uno');
    function move($c) {
        var scroll = $w.scrollTop();
        var diff = offset - scroll;
        var pos = '50% ' + (-diff)*0.5 + 'px';
        $c.css({'backgroundPosition':pos});
    }
    $w.bind('scroll', function(e){
        move($u);
    });
});