Preact and HTM example

clock.js

import { html, Component, render } from 'https://unpkg.com/htm/preact/standalone.module.js';

class Clock extends Component {
  constructor() {
    super()

    this.tick()
  }

  componentDidMount() {
    this.timer = setInterval(() => this.tick(), 1000)
  }

  tick() {
    this.setState({ time: new Date() })
  }

  componentWillUnmount() {
    clearInterval(this.timer)
  }

  render() {
    let iso8601 = this.state.time.toISOString()

    return html`<span>${iso8601}</span>`
  }
}

render(html`<${Clock} />`, document.body)