JSFiddle - React, Tailwind, and code Playground

HTML

<div id="sidebar">
    <div id="scroller">
        <p>Scroll Me!</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
        <p>Hello World</p>
       ...

CSS

#sidebar{
    width: 200px;
    height: 300px;
    border: 1px solid #000;
    overflow: hidden;
}
#sidebar #scroller{
    width: 215px;
    height: 300px;
    padding-bottom: 15px;
    overflow: scroll; 
}

JavaScript

var s = document.getElementById("sidebar");
var scroller = document.getElementById("scroller");
scroller.style.width = "150%";
s.style.width = "40px";
(function resize(i){
    if( i++ > 75 ) return;
    s.style.width = 40 + (i*4) + "px";
    setTimeout(function(){resize(i)},35);
})(0);