JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <div>
        <div>
            <div> <span>
                    <a class="child">Child</a>
                </span>

            </div>
        </div>
    </div>
</div>

JavaScript

var parent = document.querySelector('.parent'),
    child = document.querySelector('.child');

if (parent.contains(child)) {
    alert('It exists as a child.');
}