JSFiddle - React, Tailwind, and code Playground

HTML

<div id="foo"><div id="bar"></div></div>

CSS

#foo {
    position: absolute;
    top: 30px;
    left: 30px;
    border: 1px solid green;
}
#bar {
    position: relative;
    left: 30px;
    border: 1px solid red;
}

JavaScript

var offset = $('#bar').offset();
alert(offset.left + ' ' + offset.top);