JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mydiv">
    div element
</div>
<button id="btn" type="button">Check</button>

JavaScript

var element = document.getElementById('btn');

element.onclick = function() { 
    var mydiv = document.getElementById('mydiv'),
        isVisible = (mydiv.currentStyle || window.getComputedStyle(mydiv, '')).display == 'block'; 
    if (isVisible){
        mydiv.style.display = 'none';
    } else {
        mydiv.style.display = 'block';
    }
};