为什么编写完的React代码浏览器里不显示

#1
    <script type="text/babel">
        var NotesList = React.createClass({
        render: function() {
        return (
        <ol>
            {
            React.Children.map(this.props.children, function (child) {
            return
            <li>{child}</li>;
            })
            }
        </ol>
        );
        }
        });

        ReactDOM.render(
        <NotesList>
            <span>hello</span>
            <span>world</span>
        </NotesList>,
        document.getElementById('example')
        );
    </script>
</body>
</html>
#2

react里面return后面必须紧跟标签,或者用return()