Storeon

A tiny event-based Redux-like state manager for React and Preact.

• Small. 175 bytes (minified and gzipped). No dependencies. It uses Size Limit to control size.
• Fast. It tracks what parts of state were changed and re-renders only components based on the changes.
• Hooks. The same Redux reducers. Now with hooks for React/Preact.
• Modular. API created to move business logic away from React components.

import createStore from 'storeon'

// Initial state, reducers and business logic are packed in independent modules
let increment = store => {
  // Initial state
  store.on('@init', () => ({ count: 0 }))
  // Reducers returns only changed part of the state
  store.on('inc', ({ count }) => ({ count: count + 1 }))
}

export const store = createStore([increment])

import useStoreon from 'storeon/react' // or storeon/preact

export default const Counter = () => {
  // Counter will be re-render only on `state.count` changes
  const { dispatch, count } = useStoreon('count')
  return <button onClick={() => dispatch('inc')}>{count}</button>
}

import StoreContext from 'storeon/react/context'

render(
  <StoreContext.Provider value={store}>
    <Counter />
  </StoreContext.Provider>,
  document.body
)

Usage

Store

The store should be created with createStore() function. It accepts a list of the modules.

Each module is just a function, which will accept a store and bind their event listeners.

// store/index.js
import createStore from 'storeon'

import projects from './projects'
import users from './users'

export const store = createStore([projects, users])

// store/projects.js

export default store => {
  store.on('@init', () => ({ projects: [] }))

  store.on('projects/add', ({ projects }, project) => {
    return projects.concat([project])
  })
}

The store has 3 methods:

• store.get() will return current state. The state is always an object.
• store.on(event, callback) will add an event listener.
• store.dispatch(event, data) will emit an event with optional data.

Events

There are three built-in events:

• @init will be fired in createStore. The best moment to set an initial state.
• @dispatch will be fired on every store.dispatch() call. It receives an array with the event name and the event’s data. Can be useful for debugging.
• @changed will be fired every when event listeners changed the state. It receives object with state changes.

To add an event listener, call store.on() with event name and callback.

store.on('@dispatch', ([event, data]) => {
  console.log(`Storeon: ${ event } with `, data)
})

store.on() will return cleanup function. This function will remove the event listener.

const unbind = store.on('@changed', …)
unbind()

You can dispatch any other events. Just do not start event names with @.

If the event listener returns an object, this object will update the state. You do not need to return the whole state, return an object with changed keys.

// count: 0 will be added to state on initialization
store.on('@init', () => ({ users:  { } }))

Event listener accepts the current state as a first argument and optional event object as a second.

So event listeners can be a reducer as well. As in Redux’s reducers, you should change immutable.

store.on('users/save', ({ users }, user) => {
  return {
    users: { ...users, [user.id]: user }
  }
})

store.dispatch('users/save', { id: 1, name: 'Ivan' })

You can dispatch other events in event listeners. It can be useful for async operations.

store.on('users/add', async (state, user) => {
  try {
    await api.addUser(user)
    store.dispatch('users/save', user)
  } catch (e) {
    store.dispatch('errors/server-error')
  }
})

Components

For functional components, useStoreon hook will be the best option:

import connect from 'storeon/react' // Use 'storeon/preact' for Preact
const Users = () => {
  const { dispatch, users } = useStoreon('users')
  const onAdd = useCallback(user => {
    dispatch('users/add', user)
  })
  return <div>
    {users.map(user => <User key={user.id} user={user} />)}
    <NewUser onAdd={onAdd} />
  </div>
}

For class components, you can use connect() decorator.

import connect from 'storeon/react/connect' // Use 'storeon/preact/connect' for Preact

class User extends React {
  onAdd = () => {
    this.props.dispatch('users/add', user)
  }
  render () {
    return <div>
      {this.props.users.map(user => <User key={user.id} user={user} />)}
      <NewUser onAdd={this.onAdd} />
    </div>
  }
}

export default connect('users', Users)

connect() accept the list of state keys to pass into props. It will re-render only if this keys will be changed.

DevTools

Storeon supports debugging with Redux DevTools Extension.

const store = createStore([
  …
  process.env.NODE_ENV !== 'production' && require('storeon/devtools')
])

Or if you want to print events to console you can use built-in logger. It could be useful for simple cases or to investigate issue on online error trackers.

const store = createStore([
  …
  process.env.NODE_ENV !== 'production' && require('storeon/devtools/logger')
])