JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wp_bannerize-1" class="widget WPBannerizeWidget">
    1st parent
    <div class="wp_bannerize left_sidebar">
        2nd parent
        <div>
            3rd parent
                <div id="container" class="firstad">
                    [AD CODE]
                </div>
        </div>
    </div>
</div>


<div id="wp_bannerize-2" class="widget WPBannerizeWidget">
    1st parent
    <div class="wp_bannerize top_header">
        2nd parent
        <div>
            3rd parent
                <div id="container" class="secondad">
                    [AD CODE]
                </div>
        </div>
    </div>
</div>

CSS

#wp_bannerize-1 {
    background:red;
        width:200px;
    left:0;
    position:absolute;
}
#wp_bannerize-2 {
    background:yellow;
    width:200px;
    right:0;
    position:absolute;
}
#ad-notice {
    background:#222;
    color:white;
}

JavaScript

function checkads() {
    if ($('#container').height() < 50) {
        $('#container').parent().parent().prepend('<div id="ad-notice">Please support our website</div>');
    //
}
}

$(document).ready(checkads);