gistfile1.js

/** @jsx React.DOM */

var isEven = function(n) {
    return n % 2 === 0;
}

var Message = React.createClass({
    render: function() {
        return <div>{this.props.name}</div>;
    }
});

var Root = React.createClass({
    render: function() {
        var messages = [1, 2, 3, 4].map(function(x) {
            // Logic here.
            if (isEven(x)) {
                return <Message name={ x } />;
            }
        });

        // Logic-less here.
        return <div>{ messages }</div>;
    }
});

React.renderComponent(<Root />, mountNode);