How to pass variables from html script tags to the react.js DOM

index.html

<div id="container" data-stuff="my variable">
    <!-- This element's contents will be replaced with your component. -->
</div>
<script>
  window.test = "my react test";
  window.dumbname = "martin"
  // notice that `stuff` is not passed directly, it is passed using `data-stuff="my variable"` through `container.dataset` 
</script>

main.js

class Hello extends React.Component {
  render() {
    return <div>Hello {this.props.somename}. This is a {this.props.test}. 
    One can also add variables like "{this.props.stuff}" was passed using the `data-$` class</div>;
  }
}

ReactDOM.render(
  <Hello {...(container.dataset)} test={test} somename={dumbname}/>, //stuff in container
  document.getElementById('container')
);