Default props before ES6

App.js

const React = require( 'react' );
const CreateReactClass = require( 'create-react-class' );

const App = CreateReactClass( {
    getDefaultProps() {
        return {
            message: 'world'
        }
    },
    render() {
        return React.createElement( 'h1', null, `Hello ${this.props.message}` );
    }
} )

export default App;

index.js

import React from 'react';
import ReactDOM from 'react-dom';
import App from './components/App';
import App2 from './components/App2';

ReactDOM.render(
    <App/>,
    document.querySelector( '#root' )
);