JSFiddle - React, Tailwind, and code Playground

HTML

<div class="one">&nbsp;</div>
<p id="output"></p>

CSS

.one {
    margin: 20px;
    min-height: 60px;
    max-width: 220px;
    background-repeat: no-repeat;
    background-color: #FFC;
    
    background-image: url(https://developer.mozilla.org/samples/cssref/background-position/starsolid.gif);
    background-position: right bottom;
}

JavaScript

var r = $('.one').css("backgroundPositionX");
if(r === '100%')
    $('#output').html('passed');
else
    $('#output').html('failed');