JSFiddle - React, Tailwind, and code Playground

HTML

<button id="down">down</button>
<button id="down2">down2</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);
});

$('#down2').click(function() {
    var anim = $("#animated");
    var hrOff = $("#max").offset();
    var thOff = anim.offset();
    new_margin = Math.min(hrOff.top - thOff.top - anim.height(), 75);
    console.log(new_margin, hrOff.top, thOff.top);
    var st = 0;
    if (new_margin < 75) {
        st = 75 - new_margin;
        //have container scroll by this much?
    }

    anim.animate({
        marginTop: "+=" + new_margin
    }, 1000);
});