JSFiddle - React, Tailwind, and code Playground

HTML

<button class="testAdder">Add Test</button>
<p>1</p>
<img =""/ >
<ul>
<li>asdli</li>
</ul>
</ul>
<div>2</div>
<div>3</div>
<p>4</p>
<p>5</p>
<div>6</div>
<div>4</div>
<p>5</p>
<div>6</div>
<p>1</p>
<img =""/ >
<ul>
<li>asdli</li>
</ul>
</ul>
<div>2</div>
<div>3</div>
<p>4</p>
<p>5</p>
<p>6</p>
<div>4</div>
<p>5</p>
<div>6</div>
<p>1</p>
<img =""/ >
<ul>
<li>asdli</li>
</ul>
</ul>
<div>2</div>
<div>3</div>
<p>4</p>
<p>5</p>
<div>6</div>
<p>4</p>
<p>5</p>
<div>6</div>

JavaScript

var insertAfter = 3;
$(document).on('click', '.testAdder', function(){
    $('img:nth-child(' + (insertAfter) + 'n)').after('<div>TEST</div>');
});