template-element-4-1.js

// Virtual DOM example
var tree = render(count);               // We need an initial tree
var rootNode = createElement(tree);     // Create an initial root DOM node ...
document.body.appendChild(rootNode);    // ... and it should be in the document
setInterval(function () {
      count++;
      var newTree = render(count);
      var patches = diff(tree, newTree);
      rootNode = patch(rootNode, patches);
      tree = newTree;
}, 1000);

template-element-4-2.jsx

// jsx example
const element = (
  <div>
    <h1>Hello!</h1>
    <h2>Good to see you here.</h2>
  </div>
);
render(element);