01-js.html

<div id="root"></div>

<script src="http://unpkg.com/react@16.0.0/umd/react.production.min.js"></script>
<script src="http://unpkg.com/react-dom@16.0.0/umd/react-dom.production.min.js"></script>
<script type="text/javascript">

const rootElement = document.getElementById('root')

// With JS
// const domElement = document.createElement('div')
// domElement.textContent = 'Hello World'
// domElement.className = 'container'
// rootElement.appendChild(domElement)

// const domElement = React.createElement(
//   'div', //element type
//   {className: 'container'}, //props
//   'Hello World', //children prop
//   'Goodbye World' //children prop
// )

const domElement = React.createElement(
  'div', //element type
  {className: 'container', //props
  children: ['Hello World', 'Goodbye World']}, //props
)

console.log(domElement)

ReactDOM.render(domElement, rootElement)
</script>