JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main_class" id="1">
       <p>text0</p>
       <p>text0</p>
      <div class="cont" id="1-1">
       <p>text1</p>
       <p>text1</p>
       <p>text1</p>
       <p>text1</p>
       <p>text1</p>
       <p>text1</p>
      </div>
      <div class="size_fixed" id="1-2"></div>
        <div class="my"></div>
</div>


<div class="main_class" id="2">
      <div class="cont" id="2-1">
       <p>text2</p>
       <p>text2</p>
       <p>text2</p>
       <p>text2</p>
       <p>text2</p>
       <p>text2</p>
      </div>
      <div class="size_fixed" id="2-2">  
        <div class="my_2"></div>
</div>

CSS

.test {
  color:red;
}

JavaScript

$('.my').parent().addClass('rename')
 $('.rename div p').addClass('test');