JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.2.0.min.js"></script>
<div class="row"></div>
<div class="row"></div>
<div class="last"></div>
<br>
<div class="row"></div>
<div class="row"></div>
<div class="row"></div>
<div class="row"></div>
<div class="row"></div>
<div class="last"></div>
<br>
<div class="row"></div>
<div class="row"></div>
<div class="row"></div>
<div class="last"></div>

JavaScript

$("div.last").each(function() {
  $(this).prevAll(".row").addBack().wrapAll("<div class='wrapper' />");	
});