JSFiddle - React, Tailwind, and code Playground

HTML

<div class="tab-content">
  <div class='tab-pane'>1</div>
  <div class='tab-pane'>2</div>
</div>

<div class="tab-content">
  <div class='tab-pane'>1</div>
  <div class='tab-pane'>2</div>
</div>

CSS

.active {
  background-color: red;
}

JavaScript

$(".tab-content").each(function() {
  $(this).children(".tab-pane").first().addClass("active");
});