switch.jsx

const Switch = (props) => <span>{props.children}</span>;
const Case = (props) => props.expr && props.children;

function TestSwitch() {
  const val = 3;
  return (
  <Switch>
    <Case expr={val === 1}>
      <div>One</div>
    </Case>
    <Case expr={val === 2}>
      <div>Two</div>
    </Case>
    <Case expr={val === 3}>
      <div>Three</div>
    </Case>
  </Switch>
  );
}

const elem = document.getElementById('thing'); 
ReactDOM.render(<TestSwitch/>, elem)