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

JavaScript 1.7

const Parent = React.createClass({
    render() {
        const rows = [];
        let group = 1;
        for (let i = 1; i <= 12; i++) {
            rows.push(<Child key={i} id={i} group={group} />);

            if (i % 3 === 0) {
                group++;
            }
        }
        return (
            <ul>
                {rows}
            </ul>
        );
    }
});

const Child = React.createClass({
    render() {
        return (
            <li className="child">id: {this.props.id} - group: {this.props.group}</li>
        );
    }
});

ReactDOM.render(
    <Parent />,
    document.getElementById('app')
);