JSFiddle - React, Tailwind, and code Playground

HTML

<button class="popup" onclick="showpop();"><span class="popuptext" id="myPopup">HERE I AM!</span>SHOW ME A POPUP</button>

CSS

.popup {
    background-color: black;
    position: relative;
    display: inline-block;
    cursor: pointer;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    font-weight: bold;
    font-family: 'Raleway', sans-serif;
    font-size: 1em;
    text-decoration: none;
    color: green;
    float: left;
    border-radius: 5px;
    border: none;
    width: 100%;
}

:focus {
    outline: 0 !important;
}

.popup .popuptext {
    visibility: hidden;
    width: 160px;
    background-color: #555;
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 8px 0;
    position: absolute;
    z-index: 1;
    bottom: 125%;
    left: 50%;
    margin-left: -80px;
}

/* Popup arrow */
.popup .popuptext::after {
    content: "";
    position: absolute;
    top: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: #555 transparent transparent transparent;
}

.popup .show {
    visibility: visible;
    -webkit-animation: fadeIn 1s;
    animation: fadeIn 1s;
}

.popup .hide {
    visibility: hidden;
}

@-webkit-keyframes fadeIn {
    from {opacity: 0;} 
    to {opacity: 1;}
}

@keyframes fadeIn {
    from {opacity: 0;}
    to {opacity:1 ;}
}

JavaScript

function showpop() {
var popup = document.getElementById("myPopup");
          	popup.classList.toggle("show");
setTimeout(
            function() {
                popup.classList.toggle("hide");
            }, 750);
}