Function observable

Creates a RxJs style observable

const o = observable(stream => {
 // Code to run for initialisation when we go from idle to at least one subscriber
 // Won't run again for additional subscribers, but WILL run again if we lose
 // all subscribers and then get one

 // To send a value:
 stream.set(someValue);

  // Optional: return function to call when all subscribers are removed
  return () => {
    // Code to run when all subscribers are removed
  }
});
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For example:

const xy = observable<(stream => {
 // Send x,y coords from PointerEvent
 const send = (event) => {
   stream.set({ x: event.x, y: event.y });
 }
 window.addEventListener(`pointermove`, send);
 return () => {
   // Unsubscribe
   window.removeEventListener(`pointermove`, send);
 }
});

xy.onValue(value => {
 console.log(value);
});
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