Hello World

From the Hello World tutorial.

This leaves out App.jsx and rather sets up the app content directly in render.

• index.jsx

    import ReactDOM from 'react-dom';
  
    ReactDOM.render(
      <h1>Hello, World!</h1>,
      document.getElementById('root')
    );
  

Refactored to use an app as an element (just a variable, not a function) with demonstration using of substitution.

• index.jsx

    import ReactDOM from 'react-dom';
      
    const name = 'World';
    const element = <h1>Hello, { name }!</h1>;
      
    ReactDOM.render(
      element,
      document.getElementById('root')
    );