Try it online! codepan.net/gist/ca0f1001fa2a0920f892fa754e600653

codepan.json

{
  "showPans": [
    "js",
    "output"
  ],
  "activePan": "js"
}

index.html

<script src="https://unpkg.com/preact@7.2.1/dist/preact.js"></script>

index.js

/* @jsx h */
const { Component, h, render } = preact

class App extends Component {
  state = {
    count: 0
  }

  inc = () => this.setState({
    count: this.state.count + 1
  })

  dec = () => this.setState({
    count: this.state.count - 1
  })

  render() {
    return (
      <div>
        <h2>{ this.state.count }</h2>
        <button onClick={this.inc}>Increment</button>
        <button onClick={this.dec}>Decrement</button>
      </div>
    )
  }
}

render(<App />, document.body)