JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>1</li>
    <li>
        <ul>
            <li>2</li>
            <li>3</li>
        </ul>
    </li>
    <li>4</li>
</ul>

CSS

ul {
   margin: 10px;   
}

JavaScript

var ul = document.querySelectorAll("ul")[0];

[].filter.call(ul.querySelectorAll("li"), function(element) {
    return element.parentNode == ul;
}).forEach(function(element) {
    element.style.border = '1px solid #ccc';
});