JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mainDiv"> <-- I have this
    <div>
        <div>zxczxc</div>
        <div>zxczxc</div> <-- I need to get this
    </div>
    <span></span>
    <more stuff />
</div>

JavaScript

var mainDiv = document.getElementById('mainDiv');
    var div = mainDiv.getElementsByTagName('div')[2].style.display='none';//third div