JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://muut.com/riotjs/dist/demo/js/riot.js"></script>
<title>RIOT example</title>
<timetable>
    <timer></timer>
</timetable>

JavaScript

riot.tag('timer', '', function (opts) {
    this.updateHtml = () => this.root.innerHTML = 'hoge'
	this.on('update', () => this.updateHtml())
	this.updateHtml()
});

riot.mount('timer', {
    start: 0
});