Discussion on: React vs Signals: 10 Years Later

[Karl O'Keeffe]

This was an interesting challenge, as I could see lots of ways of building this in React depending on which parts of the above code were considered critical.

The most natural way I would write it is:

const One = ({count}) => {
  return <div>value in One: {count}</div>
}

const Two = ({count}) => {
  return <div>value in Two: {count * 2}</div>
}

const App = () => {
  const [count, setCount] = useState(0);
  useEffect(() => {
    setInterval(() => {
      setCount(count => count + 1);
    }, 500)
  }, []);

  return(
    <>
      <One count={count} />
      <Two count={count} />
    </>
  );
}

ReactDOM.render(<App />, document.getElementById("app"));

codepen.io/karlokeeffe/pen/vYzxPEX

The big difference with the above Solid code is that this moves the state handling into a top level React component so that React will re-render our components when the state changes.

We also need to wrap the setInterval call in a useEffect in order to kick off the interval from a React component.

[Tom Sherman]

You don't technically even need the top level App component or the state...

const One = ({count}) => {
  return <div>value in One: {count}</div>
}

const Two = ({count}) => {
  return <div>value in Two: {count * 2}</div>
}

const root = React.createRoot(document.getElementById("app"));
let count = 0;

setInterval(() => {
  count++;
  root.render(
    <>
      <One count={count} />
      <Two count={count} />
    </>,
  );
}, 500);

[Adam]

This thread is crazy.

Impure solidjs components being rebuilt using pure react components.

Let's turn this into a different challenge: write the code and the tests for each of these in solid and react

[Jin]

const [n, setN] = createSignal(0)
setInterval(() => setN(n() + 1), 500)

This code looks very simple and concise. But this is incorrect code, since the timer running will never stop. It's a time bomb. If you write this code correctly with the timer reset when removing the component, then the code will turn out to be not so concise at all. And I am silent about the fact that this code ticks not 2 times per second, but at unpredictable intervals of time, which introduces a progressive systematic error. To avoid this, you need to measure the time that has elapsed since the timer started.

In $moll there is a special store ticking with a given accuracy for this. Example:

const start = Date.now()

const { elapsed, run } = $mol_wire_let({
    elapsed: ()=> $mol_state_time.now( 1e3 ) - start,
    run: ()=> console.log( 'Elapsed: ', elapsed() / 1e3 ),
})

run()
setTimeout( ()=> run.atom.destructor(), 1e4 )