JSFiddle - React, Tailwind, and code Playground

HTML

<div id="n">
    <div class="u">
        <p>
            Text
        </p>
    </div>
    <ul>
        <li>
            <p>
                Some other text
            </p>
        </li>
    </ul>
</div>

CSS

#n{
    background-color:red;
    width:100px;
}
.u{
    background-color:blue;
}
ul{
     background-color:green;
}

JavaScript

var ulWidth = parseInt$("#u").width() * .89);
$("#n ul").width(ulWidth);