JSFiddle - React, Tailwind, and code Playground

HTML

<button id="down">down</button>
<div id="outer">
    <div id="container">
        <div id="inner">
            <div id="animated">
            </div>
        </div>
    
    </div>
    <hr id="max" />
</div>

CSS

#outer {
    position: relative;
    width: 300px;
    height: 300px;
    background-color: #eee;
}

#container {
    width: inherit;
    height: inherit;
    overflow-y: scroll;
    overflow-x: hidden;
}

#inner {
    width: 300px;
    height: 2000px;
    background-color: inherit;
}

#animated {
    margin: 50px;
    background-color: #33aa66;
    width: 50px;
    height: 50px;
}

#max {
    position: absolute;
    top: 200px;
    background-color: #aa3333;
    width: 100%;
    height: 3px;
}

JavaScript

var new_margin;
$('#down').click(function() {
    new_margin = 75 +  parseInt($('#animated').css('margin-top'));
    $("#animated").animate({marginTop: new_margin}, 1000);   
});