JSFiddle - React, Tailwind, and code Playground

HTML

<div id='sideBar' class='floating'></div>

CSS

html, body{
    border:0; margin:0; padding:0;
    min-height:1000px;
}
#container{
    height:2000px;
    width:100%;
    float:left;
    border:0; padding:0; margin:0;
}

#sideBar {
    width:50px;
    height:200px;
    background:#d22;
}
.floating{
    position:static;
    margin:100px 10px;
}
.fixed{
    position:fixed;
    top:10px; left:10px;
}

JavaScript

$(window).scroll(function(){
    
    if($(window).scrollTop() >= '90'){
        $('#sideBar').removeClass('floating');
        $('#sideBar').addClass('fixed');
    }
    
    else{
        $('#sideBar').addClass('floating');
        $('#sideBar').removeClass('fixed');
    }
});