ObservableStore

ObservableStore is a synchronous in-memory store for a single value, that you can subscribe to updates for.

Previously known as obs-store.

Usage

import { ObservableStore } from '@metamask/obs-store'

const store = new ObservableStore(initState)
store.subscribe(function showValue(value) {
  console.log('saw value:', value)
})

store.putState(5) // "saw value: 5"
store.putState(true) // "saw value: true"
store.putState({ hello: 'world' }) // "saw value: { hello: 'world' }"

console.log(store.getState().hello) // "world"

Streams

Each ObservableStore can be turned into an ObservableStoreStream. An ObservableStoreStream is a duplex stream that you can pipe new values into or pipe updated values out of.

Special behavior: Doesn't buffer outgoing updates, writes latest state to destination on pipe.

import { ObservableStore, storeAsStream } from '@metamask/obs-store'
import pump from 'pump'

const storeOne = new ObservableStore(initState)
const storeTwo = new ObservableStore()

pump(
  storeAsStream(storeOne),
  transformStream,
  storeAsStream(storeTwo)
)