JSFiddle - React, Tailwind, and code Playground

HTML

<table id="test">
    <tr>
        <td>1222</td>
    </tr>
    <tr>
        <td><span>2</span>
        </td>
    </tr>
    <tr>
        <td>3</td>
    </tr>
</table>

JavaScript

var table = document.getElementById('test'),
tr = table.getElementsByTagName('tr');

for (var i = 0; i < tr.length; ++i) {
    is_el_found = !!tr[i].getElementsByTagName('span').length;
    if (is_el_found) {
        alert(i);
    }
}