Skip to content
🐻 Bear necessities for state management in React
Branch: master
Clone or download
Latest commit b515f92 Apr 15, 2019
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
src added `shallowEqual` util from react-redux Apr 14, 2019
tests "fixed" tests while at it ;) Apr 14, 2019
.babelrc tests first draft, fix #5 Apr 13, 2019
.gitignore fix typo Apr 9, 2019
.npmignore fix typo Apr 9, 2019
.size-snapshot.json "fixed" tests while at it ;) Apr 14, 2019
LICENSE fix typo Apr 9, 2019
bear.png update bear Apr 10, 2019
package.json 0.0.5 Apr 13, 2019
readme.md Update readme.md Apr 15, 2019
rollup.config.js tests first draft, fix #5 Apr 13, 2019
setupTests.js tests first draft, fix #5 Apr 13, 2019
yarn.lock tests first draft, fix #5 Apr 13, 2019

readme.md

npm install zustand

Small, fast and scaleable bearbones state-management solution. Has a comfy api based on hooks, isn't that boilerplatey or opinionated, but still just enough to be explicit and flux-like, not context based (no reliance on providers, breaches reconciler boundaries), and is cross-platform to boot. Make your paws dirty with a small live demo here.

Create a store (or multiple, up to you...)

You could be in global or component scope, manage your store anywhere you want!

import create from 'zustand'

// Name your store anything you like, but remember, it's a hook!
const [useStore] = create(set => ({
  // Everything in here is your state
  count: 1,
  // You don't have to nest your actions, but makes it easier to fetch them later on
  actions: {
    inc: () => set(state => ({ count: state.count + 1 })), // same semantics as setState
    dec: () => set(state => ({ count: state.count - 1 })),
  },
}))

Bind components

Look Ma, no providers!

function Counter() {
  // Will only re-render the component when "count" changes
  const count = useStore(state => state.count)
  return <h1>{count}</h1>
}

function Controls() {
  // "actions" isn't special, we just named it like that to fetch updaters easier 
  const { inc, dec } = useStore(state => state.actions)
  return (
    <>
      <button onClick={inc}>up</button>
      <button onClick={dec}>down</button>
    </>
  )
}

Receipes

Fetching everything

You can, but remember that it will cause the component to update on every state change!

const data = useStore()

Selecting multiple state slices

It's just like mapStateToProps in Redux. zustand will run a small shallow equal over the object you return. Of course, it won't cause re-renders if these properties aren't changed in the state model.

const { name, age } = useStore(state => ({ name: state.name, age: state.age }))

Or, if you prefer, atomic selects do the same ...

const name = useStore(state => state.name)
const age = useStore(state => state.age)

Fetching from multiple stores

Since you can create as many stores as you like, forwarding a result into another selector is straight forward.

const currentUser = useCredentialsStore(state => state.currentUser)
const person = usePersonStore(state => state.persons[currentUser])

Memoizing selectors (this is completely optional)

You can change the selector always! But since you essentially pass a new function every render it will subscribe and unsubscribe to the store every time. Most of the time it will bearly make a difference, but when you're dealing with dozens of connected components it is a good habit to memoize your selectors with an optional second argument that's similar to Reacts useCallback. Give it the dependencies you are interested in and it will let your selector in peace, which is faster and saves memory.

const book = useBookStore(state => state.books[title], [title])

Async actions

Just call set when you're ready, it doesn't care if your actions are async or not.

const [useStore] = create(set => ({
  result: '',
  fetch: async url => {
    const response = await fetch(url)
    const json = await response.json()
    set({ result: json })
  },
}))

Read from state in actions

The set function already allows functional update set(state => result) but should there be cases where you need to access outside of it you have an optional get, too.

const [useStore] = create((set, get) => ({
  text: "hello",
  action: () => {
    const text = get().text
    ...
  }
})

Sick of reducers and changing nested state? Use Immer!

Having to build nested structures bearhanded is one of the more tiresome aspects of reducing state. Have you tried immer? It is a tiny package that allows you to work with immutable state in a more convenient way. You can easily extend your store with it.

import produce from "immer"

const [useStore] = create(set => ({
  set: fn => set(produce(fn)),
  nested: {
    structure: {
      constains: {
        a: "value"
      }
    }
  },
})

const set = useStore(state => state.set)
set(draft => {
  draft.nested.structure.contains.a.value = false
  draft.nested.structure.contains.anotherValue = true
})

Can't live without redux-like reducers and action types?

const types {
  increase: "INCREASE",
  decrease: "DECREASE"
}

const reducer = (state, { type, ...payload }) => {
  switch (type) {
    case types.increase: return { ...state, count: state.count + 1 }
    case types.decrease: return { ...state, count: state.count - 1 } 
  }
  return state
}

const [useStore] = create((set, get) => ({
  count: 0,
  dispatch: args => set(state => reducer(state, args)),
})

const dispatch = useStore(state => state.dispatch)
dispatch({ type: types.increase })

Reading/writing state and reacting to changes outside of components

You can use it with or without React out of the box.

const [, api] = create(set => ({ n: 0, setN: n => set({ n }) }))

// Getting fresh state
const n = api.getState().n
// Listening to changes
const unsub = api.subscribe(state => console.log(state.n))
// Updating state, will trigger listeners
api.getState().setN(1)
// Unsubscribing handler
unsub()
// Destroying the store
api.destroy()

Middleware

const logger = fn => {
  return (set, get) => fn(args => {
    console.log("  applying", args)
    set(args)
    console.log("  new state", get())
  }, get)
}

const [useStore] = create(logger((set, get) => {
  return { text: "hello", setText: text => set({ text }) }
}))
You can’t perform that action at this time.