JSFiddle - React, Tailwind, and code Playground

HTML

<button id="btn">Press it</button>

<div class="object">
    <div class="header">
        <span class="name">0</span>
    </div>
    <div class="children">
        <div class="string">
            <div class="header">
                <span class="name">Cheese</span>
            </div>
        </div>
    </div>
</div>

<div class="object">
    <div class="header">
        <span class="name">Biscuits</span>
    </div>
    <div class="children">
        <div class="string">
            <div class="header">
                <span class="name">Cheese</span>
            </div>
        </div>
    </div>
</div>

<div class="object">
    <div class="header">
        <span class="name">0</span>
    </div>
    <div class="children">
        <div class="string">
            <div class="header">
                <span class="name">Cheese</span>
            </div>
        </div>
    </div>
</div>

JavaScript

jQuery(function ($) {
    $('#btn').click(function () {
        jQuery('.object').each(function() {    
            if ( $.isNumeric($(this).find('.name:first').text().match(/\d+/)) ) {
                alert($(this).find('.name:first').text().match(/\d+/));
                $(this).find('div.children').find(' span.name').text($(this).find('.name:first').text().match(/\d+/));;    
            }
        });
    });
});