JSFiddle - React, Tailwind, and code Playground
HTML
<div id="unhide" style="display:none;">DUMMY TEXT</div>
<button id="expand" name="expand">Show The Div</button>
JavaScript
document.getElementById("expand").addEventListener("click", function()
{
if(document.getElementById('unhide').style.display == 'block')
document.getElementById('unhide').style.display = 'none';
else
document.getElementById('unhide').style.display = 'block';
});