JSFiddle - React, Tailwind, and code Playground

HTML

<div>Class added and removed here.</div>
<div>Class toggled here</div>
<div class="popup" onclick="myPopFunction(this)" id="myPop1">
  	<img src="Images/Slightly%20Smile.png" width="15">
  	<span class="popupimage" id="myPop1a">
  	<div style="position: relative;">
		<img src="Images/dilbert_agile_programming.gif">
		<img src="Images/Cross%20hair%20white%20border%20small.png" class="dropshadow" width="25">
	</div>
  	</span>
</div>

CSS

.dropshadow {
	border-radius:50%; 
	box-shadow: 5px 5px 3px #888888;
	position:absolute;
	top:-10px; 
	right:-10px;	
}

.popup {
    position: relative;
    display: inline-block;
    cursor:pointer;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}
.popup .popupimage {
    visibility: hidden;
    position: absolute;
    z-index: 1;
    top:100%;
    left: -320px;
}
.popup .showpop {
    visibility: visible;
    -webkit-animation: fadeIn 1s;
    animation: fadeIn 1s;
}

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

JavaScript

function classList (el) {
    function classMatch (className) {
        return new RegExp("(^\\s*|\\s+)" + className + "(\\s*$|\\s+)");
    }
    if (el.hasOwnProperty('classList')) {
        return el.classList;
    }
    return {
        add : function (className) {
            if (!this.contains(className)) {
                el.className += ' ' + className;
            }
        },
        remove : function (className) {
            el.className = el.className.replace(classMatch(className), ' ');
        },
        contains : function (className) {
            return classMatch(className).test(el.className);
        },
        toggle : function (className) {
            if (this.contains(className)) {
                this.remove(className);
            } else {
                this.add(className);
            }
        }
    };
}

function myPopFunction(elem) {
    var popup = document.getElementById(elem.id+"a");
  classList(popup).toggle("showpop");
}