JSFiddle - React, Tailwind, and code Playground

HTML

<div class="ico" onclick='AdaptiveMenu'>
  <div class="rect"></div>
  <div class="rect"></div>
  <div class="rect"></div>
</div>

<nav class="menu" id="menu">
  <ul>
    <li>lit-item</li>
    <li>lit-item</li>
    <li>lit-item</li>
    <li>lit-item</li>
  </ul>
</nav>

CSS

.ico {
  margin-left: 20px;
}
.rect {
  width: 30px;
  height: 6px;
  background-color: black;
  margin-top: 3px;
}

.menu {
  display:none;
}

JavaScript

function AdaptiveMenu() {
	var Adaptive = document.getElementById('menu');
	var AdaptiveStyle = getComputedStyle(Adaptive);
	if (AdaptiveStyle.display == 'none') {
		AdaptiveStyle.display == 'block';
	};
}