JSFiddle - React, Tailwind, and code Playground

by David Thomas

HTML

<span id="test">testing</span>

CSS

#test {
    background-color: #5AD9C1;
}

#test.on {
    background-color: #66FF66;
}

JavaScript

function toggleClass(elem, cssClassOn) {
    var currentClasses = elem.className,
        test = currentClasses.indexOf(cssClassOn) > -1;
    
    if (test) {
        elem.className = currentClasses.replace(cssClassOn,'');
    }
    else {
        elem.className += currentClasses + ' ' + cssClassOn;
    }
}

document.getElementById('test').addEventListener('click', function (e) {
    toggleClass(e.target, 'on');
});