React Base Fiddle (JSX)

Starting point for creating JSFiddles with React. This uses React with Addons.

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.24/browser.js"></script>
<script src="https://npmcdn.com/react@latest/dist/react-with-addons.js"></script>
<script src="https://npmcdn.com/react-dom@latest/dist/react-dom.js"></script>
<script src="https://facebook.github.io/react/js/jsfiddle-integration-babel.js"></script>

<div id="container">
    <!-- This element's contents will be replaced with your component. -->
</div>

JavaScript 1.7

class CounterService {
  constructor() {
    this.counter = 0
    this.observers = []
    this.tic = this.tic.bind(this)
    this.subscribe = this.subscribe.bind(this)
    this.notify = this.notify.bind(this)
    this.notifyAll = this.notifyAll.bind(this)
    setInterval(this.tic, 1000)
  }
  
  subscribe(observer) {
    this.observers.push(observer)
    this.notify(observer)
  }
  
  notify(observer) {
  	observer.next(this.counter)
  }
  
  notifyAll() {
    this.observers.forEach(this.notify)
  }
  
  tic() {
  	this.counter += 1
    this.notifyAll()
    console.log(this.counter)
  }
  
}

const ServiceSingleton = new CounterService()

class Counter extends React.Component {

	constructor(props){
    super(props)
    this.state = {
      counter: 0
    }
  }

  componentDidMount() {
  	ServiceSingleton.subscribe({
      next: counter => this.setState({ counter })
    })
  }

  render() {
    return <div>You're looking at this counter since {this.state.counter}s</div>;
  }
}

class Counter2 extends React.Component {

	constructor(props){
    super(props)
    this.state = {
      counter: 0
    }
  }

  componentDidMount() {
  	ServiceSingleton.subscribe({
      next: counter => this.setState({ counter })
    })
  }

  render() {
    return <div>You're looking at this counter 2 since {this.state.counter}s</div>;
  }
}

const Demo = () => {
 return <div><Counter/><Counter2/></div>
}

ReactDOM.render(
  <Demo />,
  document.getElementById('container')
);