Basic React rendering by listener.

BasicReactRenderingByListener.js

//Some store thing that has onUpdate as a method for setting listeners.
store.onUpdate(function(newState) {
    ReactDOM.render(
        <App state={newState} />,
        document.getElementById("root")
    );
});

//You either need to call render once here to get things started, or cause a state update.
ReactDOM.render(
    <App state={store.getState()} />,
    document.getElementById("root")
);