Result

jQueryのコードがあれば自動でbodyにclassが付く。bodyにclass与えれば親要素として指定できますね。

jQuery

$('body').addClass('use-jquery');

css

.use-jquery{background:green;}

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Warning: include(): Failed opening '/home/youhei0828/kachibito.net/public_html/wp-content/themes/cocoon-master/my-php/jquery-other-snippets.php' for inclusion (include_path='.:/opt/php-8.1.29/data/pear') in /home/youhei0828/kachibito.net/public_html/wp-content/themes/kachibito7_with_cocoon_child/functions-module/shortcode/add-post-myphp.php on line 7