JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="parent">
enfant
  <p class="enfant merci">
    merci
  </p>
  <p class="enfant">
    hello
  </p>
</div>

CSS

.active {
  background-color: green;
}

JavaScript

$(document).ready(function(){
	$('.parent').find('p:contains("merci")').addClass('active');
});