JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="nav">
  <li><a href="index.html" id="tab">Home</a></li>
  <li><a href="about.html">About</a></li>
  <li><a href="contact.html">Contact</a></li>
</ul>

CSS

#nav {
  height: 100px;
  width: 500px;
  border: 1px solid black;
}
.navUL li {
  border: 1px solid blue;
}

JavaScript

var listItems = document.querySelectorAll("ul#nav > li");
for(var l = 0; l < listItems.length; l++) {
  listItems[l].style.height = Math.floor(100/listItems.length) + "px";
}