storelax

An easy, async-friendly object store.

import { Store } from 'storelax';

const store = new Store({ animal: 'zebra' });

// Listeners are sent the current data
store.listen(state => {
  console.log(`Username: ${state.animal}`);
});

// Updates are sent to listeners
store.update({ animal: 'hippopotamus' });

Install

npm install storelax

API

new Store(source?)

Creates a new store. If source is not undefined or null, the keys of the source are used to initialized the store.

// Creating an empty store
const storeA = new Store();

// Creating a store with initial data
const storeB = new Store({ name: 'Hamilton' });

store.state

Gets the current state of the store.

const store = new Store({ color: 'purple' });

console.log(
  store.state.color // "purple"
);

store.stream

Gets a event stream for updates to the store.

const store = new Store(1);

store.stream.map(x => 2 * x).listen(x => {
  console.log(x); // Log the doubles of the store value
});

store.map(fn)

Returns a stream for updates to the store, mapped using fn.

const store = new Store(1);

store.map(x => 2 * x).listen(x => {
  console.log(x); // Log the doubles of the store value
});

store.update(source?)

Updates the store with source and notifies all listeners. If source is not undefined or null, the keys of source are used to update the store.

const store = new Store({ name: 'Amy', score: 100 });

store.update({ score: 200 });

console.log(store.state); // { name: "Amy", score: 200 }

store.listen(callback)

Adds a listener to the data store. The function callback is asynchronously called with the current state. Each time the store is updated, callback is called with the current state.

Returns a function which may be used to cancel the listener.

const store = new Store({ name: 'Mr. X' });

// "Mr. X" is logged asynchronously
const cancel = store.listen(data => {
  console.log(data.name);
});

queueMicrotask() => {
  // "Mr. Y" is logged immediately on update
  store.update({ name: "Mr. Y" });

  // Stop listening
  cancel();
});

store.wakeCallback()

Called when the first observer is attached to the store. Subclasses can override this function to allocate resources when the store is given a first listener.

store.sleepCallback()

Called when the last observer has been removed from the store. Subclasses can override this function to finalize resources when the store has no listeners.

class CounterStore extends Store {
  constructor() {
    super({ count: 0 });
    this.interval = 0;
  }

  increment() {
    let { count } = this.read();
    this.update({ count: count + 1 });
  }

  wakeCallback() {
    this.interval = setInterval(() => {
      this.increment();
    }, 1000);
  }

  sleepCallback() {
    clearInterval(this.interval);
    this.interval = 0;
  }
}