JSFiddle - React, Tailwind, and code Playground

by slove

HTML

<ul id="results"></ul>

CSS

#results li.pass {
    color: green;
}
#results li.fail {
    color: red;
    text-decoration:line-through
}

JavaScript

function assert(value, desc) {
    var li = document.createElement("li");
    li.className = value ? 'pass' : 'fail';
    li.appendChild(document.createTextNode(desc));
    document.getElementById('results').appendChild(li);
}

var Person = Object.subClass({
    init: function (isDancing) {
        this.dancing = isDancing;
    },
    dance: function () {
        return this.dancing;
    }
});
var person = new Person(true);
assert(person.dance(), 'This person is dancing');