const App = createComponent(() => {  
  const divEl$ = observable(null);
  
  // Do something any time our "ref" changes
  observe(divEl$, (divEl) => {
    console.log(divEl)
  });
  
  return (props, state) => (
    <div ref={divEl$.set}>
      {/*...*/}
    </div>
  );
});