@kingstinct/observable

Easy-to-use and dependency-free observable library. await a specific value. Observe value changes. And if you use React there is a hook.

Examples

waitFor

Network Status

const networkStatus = observable('cellular');

// ...

await networkStatus.waitFor('wifi');
console.log('Start downloading large file..');
downloadLargeFile();

// ...

networkStatus.set('wifi');      // Start downloading large file..

observe

Observe as the value changes

const networkStatus = observable('cellular');

// ...

networkStatus.observe((status, previousStatus) => {
  console.log('NetworkStatus changed from ' + previousStatus + ' to ' + status)
});

// ...

networkStatus.set('wifi');      // NetworkStatus changed from cellular to wifi
networkStatus.set('offline');   // NetworkStatus changed from wifi to offline

Set with previous value

Easy to keep it clean and immutable.

Toggle

const isSyncEnabled = observable(false);

// ...

await isSyncEnabled.waitFor(true);
updateUI();
syncChanges();

// ...

const toggleSync = (previousValue) => !previousValue
isSyncEnabled.set(toggleSync);

Press button 10 times

const buttonPresses = observable(0);

// ...

await buttonPresses.waitFor(10);

// ...

function onClick(){
  buttonPresses.set(value => value + 1);
}

Works great with React!

No need to complicate things. We provide a hook - and it works exactly like setState does - directly tied to the backing observable.

import { useObservable } from '@kingstinct/observable/react';

const clickObservable = observable(0);

const MyComponent = () => {
  const [clickCount, setClickCount] = useObservable(clickObservable);

  const onClick = () => setClickCount((previous) => previous + 1);

  return <Button onClick={onClick}>{ clickCount }</Button>
}

Bring your own Promise library

By default native JavaScript Promises are used. But you can override it if you want:

observable.Promise = bluebird; // use Bluebird instead of native promise

const isOnlineObservable = observable(false);

await isOnlineObservable.waitFor(true).timeout(1000); // use Bluebird.timeout