JSFiddle - React, Tailwind, and code Playground

HTML

<a href="#" id="menuExpand">Menu</a>
<ul class="menu">
    <li><a href="#">Menu item 1</a></li>
    <li><a href="#">Menu item 2</a></li>
    <li><a href="#">Menu item 3</a></li>
    <li><a href="#">Menu item 4</a></li>
    <li><a href="#">Menu item 5</a></li>
</ul>

CSS

* { 
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    padding: 0;
    margin: 0;
}
.menu {
    list-style: none;
}
.menu li {
    display: inline-block;
}
.menu li a {
    display: block;
    text-decoration: none;
    color: #fff;
    padding: 5px;
    border-radius: 3px;
    background-color: rgba(0, 0, 0, 1);
    border: 1px solid #fff;
}
.menu li a:hover {
    color: #000;
    background-color: #fff;
    border: 1px solid #000;
}
#menuExpand {
    display: none;
    color: #fff;
    background-color: #000;
    text-decoration: none;
    padding: 5px;
    text-align: center;
}
#menuExpand:hover {
    color: #000;
    background-color: #fff;
    border-bottom: 1px solid #000;
}
@media only screen and (max-width: 767px) {
    .menu {
        max-height: 0;
        overflow: hidden;
        width: 100%;
        -webkit-transition: max-height 0.3s;
        -moz-transition: max-height 0.3s;
        -ms-transition: max-height 0.3s;
        -o-transition: max-height 0.3s;
        transition: max-height 0.3s;
    }
    .menu li {
        display: block;
    }
    .menu li a {
        border: none;
        text-align: center;
        border-radius: 0;
    }
    #menuExpand {
        display: block;
    }
    .menuOpen {
        max-height: 1000px;
        -webkit-transition: max-height 0.5s;
        -moz-transition: max-height 0.5s;
        -ms-transition: max-height 0.5s;
        -o-transition: max-height 0.5s;
        transition: max-height 0.5s;
    }
}

JavaScript

var menu, menuExpand;

menu = document.getElementsByClassName("menu")[0];
menuExpand = document.getElementById("menuExpand");

menuExpand.onclick = function (e) {
    menu.classList.toggle("menuOpen");
}