Install

npm i @bit-about/state

Features

• 100% Idiomatic React
• 100% Typescript with state types deduction
• Efficient sub-states selectors
• Get state from a hook...
• ...or utilise static access
• No centralized state provider
• Tiny - only 1.4kB
• Just works ™

➡️ Check demo

Usage

import * as React from 'react'
import { state } from '@bit-about/state'

// 1️⃣ Create a hook-based store
const [Provider, useStore] = state(
  () => {
    const [alice, setAlice] = React.useState('Alice')
    return { alice, setAlice }
  }
)

// 3️⃣ Use the selector hook in component
const Child = () => {
  const alice = useStore(state => state.alice)
  return <p>{alice}</p>
}

// 2️⃣ Wrap tree with Provider
const App = () => (
  <Provider>
    <Child />
  </Provider>
)

State selectors

Access fine-grained control to the specific part of your state to re-render only when necessary.

// 👍 Re-render when anything changed
const { alice, bob } = useStore()

// 💪 Re-render when alice changed
const alice = useStore(state => state.alice)

// 🤌 Re-render when alice or bob changed
const [alice, bob] = useStore(state => [state.alice, state.bob])

// or
const { alice, bob } = useStore( 
  state => ({ alice: state.alice, bob: state.bob }) 
)

NOTE: Values in objects and arrays created on the fly are shallow compared.

Static store

The third element of the state() result tuple is a store object. Store is a static helper which provides access to the state without a hook.

const [Provider, useStore, store] = state(...)

and then

// 👍 Get whole state
const { alice } = store.get()

// 💪 Get substate
const alice = store
  .select(state => state.alice)
  .get()

// 🤌 Subscribe to the store and listen for changes
const subscriber = store
  .select(state => state.alice)
  .subscribe(alice => console.log(alice))
  
// remember to unsubscribe!
subscriber.unsubscribe()

NOTE: It's not necessary to fetch state inside the Provider - but it still needs to be placed somewhere to init the state.

State props

The state hook allows you to pass any arguments into the context. It can be some initial state or you could even return it and pass it through to the components. All state prop changes will update the context and trigger component re-rendering only when necessary.

const [UserProvider, useUser] = state(
  ({ id }) => {
    const [user] = React.useState(() => getMyUserBy(id))
    return user
  }
)

const UserProfile = ({ id }) => (
  <UserProvider id={id}>
    ...
  </UserProvider>
)

👉 Functions in state

Please remember that functions defined without React.useCallback create themselves from scratch every time - which results in incorrect comparisons and components think the state has changed so they re-render themselves.

const [Provider, useStore] = state(
  () => {
    const [counter, setCounter] = React.useState(0);
   
    // ✖️ It will re-render components every time
    // const incrementCounter = () => setCounter(value => value + 1)

    const incrementCounter = React.useCallback(
      () => setCounter(value => value + 1),
      [setCounter]
    )

    return { counter, incrementCounter }
  }
)

BitAboutState 💛 BitAboutEvent

Are you tired of sending logic to the related components? Move your bussiness logic to the hook-based state using @bit-about/state + @bit-about/event.

Now you've got completely type-safe side-effects. Isn't that cool?

import { state } from '@bit-about/state'
import { useEvent } from './auth-events' // Hook generated from events()
import User from '../models/user'

const [UserProvider, useUser] = state(
  () => {
    const [user, setUser] = React.useState<User | null>(null)
    
    useEvent({
      userLogged: (user: User) => setUser(user),
      userLoggout: () => setUser(null)
    })
    
    return user
  }
)

BitAboutState 💛 React Query

import { useQuery } from 'react-query'
import { fetchUser } from './user'

const [UserProvider, useUser] = state(
  ({ id }) => {
    const { data: user } = useQuery(['user', id], () => fetchUser(id))
    return user
  }
)

const UserProfile = ({ id }) => (
  <UserProvider id={id}>
    ...
  </UserProvider>
)

// 🧠 Re-render ONLY when user avatar changed (no matter if isLoading changes)
const avatar = useUser(state => state.user.avatar)

Partners

Credits

• Constate - approach main inspiration
• use-context-selector & FluentUI - fancy re-render avoiding tricks and code main inspiration

License

MIT © Maciej Olejnik 🇵🇱

Support me

If you use my library and you like it... it would be nice if you put the name BitAboutState in the work experience section of your resume. Thanks 🙇🏻!