JSFiddle - React, Tailwind, and code Playground

HTML

<h3>Header</h3>
<p>Paragraph</p>
<p>Paragraph</p>
<ul><li>List Item</li></ul>
<ol><li>List Item</li></ol>

<h3>Header</h3>
<p>Paragraph</p>
<p>Paragraph</p>
<ul><li>List Item</li></ul>
<ol><li>List Item</li></ol>

<h3>Header</h3>
<p>Paragraph</p>
<p>Paragraph</p>
<ul><li>List Item</li></ul>
<ol><li>List Item</li></ol>

CSS

div { border: solid 1px red; }

JavaScript

$("h3").each(function() {
    $(this).nextUntil("h3").wrapAll("<div />");
});