pure-undo-store

Just edit your app's state.

pure-undo-store is a fast, simple, immutable store that lets you update state directly (i.e. imperatively). It also works excellently with typescript.

Comparison with redux

With React Hooks

pure-undo-store can be used without react, but if you are using react you can use the usePureStore hook. We could create the simple counter from the image above like this:

import createStore from "pure-undo-store/react"

const store = createStore({ count: 0 })

export default ()=> {
  const [state, update] = store.usePureStore()

  return (
    <div>
      Counter: { state.count }
      <a onClick={()=> update({count: count+1})}> + </a>
      <a onClick={()=> update({count: count-1})}> - </a>
    </div>
  )
}

If you use react, then congratulations - you know everything you need to to manage state in your app. Because the data is updated immutably, you can pass pieces of the store's state to your React.memo components and they will re-render only when the data has changed giving you excellent performance.

Without Hooks

To use pure-undo-store without react hooks you need to create a store, and know how to use a couple of methods.

createStore(initialState)

Creates a new store with an initial state. You can create multiple independent stores, although usually one is enough.

import createStore from 'pure-undo-store'

const store = createStore({ count: 0 })

If you're using typescript, you can get type checking and autocompletion automatically with the rest of your pure-undo-store usage:

interface State {
  user: User
  messages: {
    user: User
    text: string
    starred?: boolean
  }[]
  lastMessageAt?: Date
  messageCount: number
}

const state: State = {
  user: getUser(),
  messages: []
}

const store = createStore(state)

state / getState()

Returns the current state from the store.

console.log("last message date:", store.getState().lastMessageAt)

const Messages = ()=> {
  const { user, messages, lastMessageAt } = store.state

  return (
    <div>
      <h3>Messages for {user.name}</h3>
      <ul>
        {
          messages.map(m=> (
            <Message message={m} />
          ))
        }
      </ul>
    </div>
  )
}

update(updater)

Use this anytime you want to update store data. The updater argument can either be an object in which case it works just like react's setState, or it can be a function, in which case it's given a copy of the state which can be modified directly.

store.update({ lastMessageAt: new Date() })

store.update(s=> {
  s.messageCount++
  s.messages.push(message)
  s.lastMessageAt = new Date()
})

subscribe(callback)

To re-render components when you update the store, you should subscribe to the store. The subscribe method takes a callback that takes no arguments. It returns a method to remove that subscription. You can subscribe many times to one store.

The recommended way is to re-render your whole app - pure-undo-store can make this very efficient because immutable state lets you use React.PureComponent classes.

const render = ()=> {
  ReactDOM.render(<App />, document.getElementById('root'))
}

store.subscribe(render)
render()

You could also use forceUpdate within a component e.g.:

class App extends React.Component {
  constructor() {
    store.subscribe(()=> this.forceUpdate())
  }
  //...

bonus: storeFor(getter), updaterFor(getter), and usePureStore(getter)

These methods let you define a subset of the store as a shortcut, so you don't have to reference the whole chain every time.

console.log(store.user.profile.address.city)
store.update(s=> s.user.profile.address.city = "Wellington")

// vs
const addressStore   = store.storeFor(s=> s.user.profile.address)
const addressUpdater = store.updaterFor(s=> s.user.profile.address)

// and then:
console.log(addressStore.state.city)
addressUpdater(a=> a.city = "Wellington")

Which can be useful in larger projects.

Patterns

Actions

Other state management libraries have a concept of using 'actions' and 'action creators' for controlled state updates. You may well find them unnecessary, but if you miss them, you can easily do something similar:

// actions.js
import store from './store'
export function postMessage(text) {
  store.update(s=> {
    s.messages.push({
      user: s.user,
      text
    })
    s.lastMessageAt = new Date()
  })
}

// component.js
  //...
  <button onClick={()=> postMessage(this.props.text)} />
  //...

Persistence

If you want to persist data between sessions, it can be done very simply. You just need a way to serialize and de-serialize your data. If you use only basic data types, you can use JSON.stringify and JSON.parse:

const STORAGE_KEY = "myapp-data"
const storedData = JSON.parse(localStorage.getItem(STORAGE_KEY))

const store = createStore(storedData || getDefaultData())

window.addEventListener("beforeunload", ()=> {
  localStorage.setItem(STORAGE_KEY, JSON.stringify(store.state))
})

Future

pure-undo-store is stable now, and I do not anticipate a need to change the API. The focus for now is improving the documentation.