explain why you may want to return a function from a resource, instead of just returning a value.

[NullVoxPopuli]

Example:

const Clock = resource(({ on }) => {
  const now = cell(Date.now());
  const interval = setInterval(() => now.current = Date.now(), 1000);
  on.cleanup(() => clearInterval(interval));

  return now.current;
})

vs

const Clock = resource(({ on }) => {
  const now = cell(Date.now());
  const interval = setInterval(() => now.current = Date.now(), 1000);
  on.cleanup(() => clearInterval(interval));

  return () => now.current;
})

The reason:

• because the tracked data (.current), would be immediately consumed in the resource() body, the whole thing would be torn down when the clock updates (create a new interval each second). By using a function, only the function invalidates, you retain state, and keep the interval.