4.0.0 • Public • Published

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A tiny 350b centralized state container with component bindings for Preact & React.

  • Small footprint complements Preact nicely (unistore + unistore/preact is ~650b)
  • Familiar names and ideas from Redux-like libraries
  • Useful data selectors to extract properties from state
  • Portable actions can be moved into a common place and imported
  • Functional actions are just reducers
  • NEW: seamlessly run Unistore in a worker via Stockroom

Table of Contents


This project uses node and npm. Go check them out if you don't have them locally installed.

npm install --save unistore

Then with a module bundler like webpack or rollup, use as you would anything else:

// The store:
import createStore from 'unistore'

// Preact integration
import { Provider, connect } from 'unistore/preact'

// React integration
import { Provider, connect } from 'unistore/react'

Alternatively, you can import the "full" build for each, which includes both createStore and the integration for your library of choice:

import { createStore, Provider, connect } from 'unistore/full/preact'

The UMD build is also available on unpkg:

<!-- just unistore(): -->
<script src="https://unpkg.com/unistore/dist/unistore.umd.js"></script>
<!-- for preact -->
<script src="https://unpkg.com/unistore/full/preact.umd.js"></script>
<!-- for react -->
<script src="https://unpkg.com/unistore/full/react.umd.js"></script>

You can find the library on window.unistore.


import createStore from 'unistore'
import { Provider, connect } from 'unistore/preact'

let store = createStore({ count: 0, stuff: [] })

let actions = {
  // Actions can just return a state update:
  increment(state) {
    // The returned object will be merged into the current state
    return { count: state.count+1 }

  // The above example as an Arrow Function:
  increment2: ({ count }) => ({ count: count+1 }),

  // Actions receive current state as first parameter and any other params next
  // See the "Increment by 10"-button below
  incrementBy: ({ count }, incrementAmount) => {
    return { count: count+incrementAmount }

// If actions is a function, it gets passed the store:
let actionFunctions = store => ({
  // Async actions can be pure async/promise functions:
  async getStuff(state) {
    const res = await fetch('/foo.json')
    return { stuff: await res.json() }

  // ... or just actions that call store.setState() later:
  clearOutStuff(state) {
    setTimeout(() => {
      store.setState({ stuff: [] }) // clear 'stuff' after 1 second
    }, 1000)

  // Remember that the state passed to the action function could be stale after
  // doing async work, so use getState() instead:
  incrementAfterStuff(state) {
    const res = await fetch('foo.json')
    const resJson = await res.json()
    // the variable 'state' above could now be old,
    // better get a new one from the store
    const upToDateState = store.getState()

    return {
      stuff: resJson,
      count: upToDateState.count + resJson.length,

// Connecting a react/preact component to get current state and to bind actions
const App1 = connect('count', actions)(
  ({ count, increment, incrementBy }) => (
      <p>Count: {count}</p>
      <button onClick={increment}>Increment</button>
      <button onClick={() => incrementBy(10)}>Increment by 10</button>

// First argument to connect can also be a string, array or function while
// second argument can be an object or a function. Here we pass an array and
// a function.
const App2 = connect(['count', 'stuff'], actionFunctions)(
  ({ count, stuff, getStuff, clearOutStuff, incrementAfterStuff }) => (
      <p>Count: {count}</p>
        <ul>{stuff.map(s => (
      <button onClick={getStuff}>Get some stuff!</button>
      <button onClick={clearOutStuff}>Remove all stuff!</button>
      <button onClick={incrementAfterStuff}>Get and count stuff!</button>

export const getApp1 = () => (
  <Provider store={store}>
    <App1 />

export const getApp2 = () => (
  <Provider store={store}>
    <App2 />


Make sure to have Redux devtools extension previously installed.

import createStore from 'unistore'
import devtools    from 'unistore/devtools'

let initialState = { count: 0 };
let store = process.env.NODE_ENV === 'production' ?  createStore(initialState) : devtools(createStore(initialState));

// ...


README Example on CodeSandbox



Creates a new store, which is a tiny evented state container.


  • state Object Optional initial state (optional, default {})


let store = createStore();
store.subscribe( state => console.log(state) );
store.setState({ a: 'b' });   // logs { a: 'b' }
store.setState({ c: 'd' });   // logs { a: 'b', c: 'd' }

Returns store


An observable state container, returned from createStore


Create a bound copy of the given action function. The bound returned function invokes action() and persists the result back to the store. If the return value of action is a Promise, the resolved value will be used as state.


  • action Function An action of the form action(state, ...args) -> stateUpdate

Returns Function boundAction()


Apply a partial state object to the current state, invoking registered listeners.


  • update Object An object with properties to be merged into state
  • overwrite Boolean If true, update will replace state instead of being merged into it (optional, default false)

Register a listener function to be called whenever state is changed. Returns an unsubscribe() function.


  • listener Function A function to call when state changes. Gets passed the new state.

Returns Function unsubscribe()


Remove a previously-registered listener function.


  • listener Function The callback previously passed to subscribe() that should be removed.

Retrieve the current state object.

Returns Object state


Wire a component up to the store. Passes state as props, re-renders on change.


  • mapStateToProps (Function | Array | String) A function mapping of store state to prop values, or an array/CSV of properties to map.
  • actions (Function | Object)? Action functions (pure state mappings), or a factory returning them. Every action function gets current state as the first parameter and any other params next


const Foo = connect('foo,bar')( ({ foo, bar }) => <div /> )
const actions = { someAction }
const Foo = connect('foo,bar', actions)( ({ foo, bar, someAction }) => <div /> )

Returns Component ConnectedComponent


Extends Component

Provider exposes a store (passed as props.store) into context.

Generally, an entire application is wrapped in a single <Provider> at the root.


  • props Object
    • props.store Store A {Store} instance to expose via context.

Reporting Issues

Found a problem? Want a new feature? First of all, see if your issue or idea has already been reported. If not, just open a new clear and descriptive issue.


MIT License © Jason Miller

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