JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" id="myCheck"  onclick="addbox();">Add new item type
    
<div class="row" id="area" style="display: none;" >
    Something
</div>

JavaScript

document.getElementById("myCheck").addEventListener("click", function() {
    toggle('area');
});

function toggle(obj) {

	var el = document.getElementById(obj);

	el.style.display = (el.style.display != 'none' ? 'none' : '' );

}