StoneCypher's external state example, re-written for React latest (15.x)

foo.jsx

let counter = 0;
const repaint = () => React.render(<Spinner data={counter}/>, document.body);
const inc     = () => { counter += 1, repaint() };
const dec     = () => { counter -= 1, repaint() };

const Spinner = ({ counter }) => (
    <div>
        {counter}
        <button value="^" onclick={inc}/>
        <button value="v" onclick={dec}/>
    </div>
);