const addScripts = () => {
  ReactDOM.render(React.createElement(App), document.getElementById("uiApp"));
};

const Greeter = () => {
  return (
    <div className="background">
      <button onClick={addScripts}>Let's start watching!</button>
    </div>
  );
};

ReactDOM.render(React.createElement(Greeter), document.getElementById("uiApp"));