jotai

Primitive, flexible state management for React.

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Jotai is pronounced "joe-tie" and means "state" in Japanese.

How does Jotai differ from Recoil?

  • Minimalistic API
  • No string keys
  • TypeScript oriented

doc.01

An atom represents a piece of state. All you need is to specify an initial value, which can be primitive values like strings and numbers, objects and arrays. You can create as many primitive atoms as you want.

import { atom } from 'jotai'

const countAtom = atom(0)
const countryAtom = atom("Japan")
const citiesAtom = atom(["Tokyo", "Kyoto", "Osaka"])
const mangaAtom = atom({ "Dragon Ball": 1984, "One Piece": 1997, "Naruto": 1999 })
React JSX

doc.02

You can only use atoms under this component tree.

import { Provider } from 'jotai'

const Root = () => (
  <Provider>
    <App />
  </Provider>
)
React JSX

doc.03

It can be used just like React.useState:

import { useAtom } from 'jotai'

function Counter() {
  const [count, setCount] = useAtom(countAtom)
  return (
    <h1>
      {count}
      <button onClick={() => setCount(c => c + 1)}>one up</button>
React JSX

doc.04

A new read-only atom can be created from existing atoms by passing a read function as the first argument. get allows you to fetch the contextual value of any atom.

const doubledCountAtom = atom(get => get(countAtom) * 2)

function DoubleCounter() {
  const [doubledCount] = useAtom(doubledCountAtom)
  return <h2>{doubledCount}</h2>
React JSX

rec.00

rec.01

You can combine multiple atoms to create a derived atom.

const count1 = atom(1)
const count2 = atom(2)
const count3 = atom(3)

const sum = atom(get => get(count1) + get(count2) + get(count3))
React JSX

Or if you like fp patterns ...

const atoms = [count1, count2, count3, ...otherAtoms]
const sum = atom(get => atoms.map(get).reduce((acc, count) => acc + count))
React JSX

rec.02

You can make the read function an async function, too.

const urlAtom = atom("https://json.host.com")
const fetchUrlAtom = atom(
  async get => {
    const response = await fetch(get(urlAtom))
    return await response.json()
  }
)

function Status() {
  // Re-renders the component after urlAtom changed and the async function above concludes
  const [json] = useAtom(fetchUrlAtom)
React JSX

rec.03

Specify a write function at the second argument. get will return the current value of an atom, set will update an atoms value.

const decrementCountAtom = atom(
  get => get(countAtom),
  (get, set, _arg) => set(countAtom, get(countAtom) - 1),
)

function Counter() {
  const [count, decrement] = useAtom(decrementCountAtom)
  return (
    <h1>
      {count}
      <button onClick={decrement}>Decrease</button>
React JSX

rec.04

Just do not define a read function.

const multiplyCountAtom = atom(null, (get, set, by) => set(countAtom, get(countAtom) * by))

function Controls() {
  const [, multiply] = useAtom(multiplyCountAtom)
  return <button onClick={() => multiply(3)}>triple</button>
React JSX

rec.05

Just make the write function an async function and call set when you're ready.

const fetchCountAtom = atom(
  get => get(countAtom),
  async (_get, set, url) => {
    const response = await fetch(url)
    set(countAtom, (await response.json()).count)
  }
)

function Controls() {
  const [count, compute] = useAtom(fetchCountAtom)
  return <button onClick={() => compute("http://count.host.com")}>compute</button>
React JSX

GitHub

pmndrs/jotai

19724658

👻 Primitive and flexible state management for React — Read More

https://jotai.org

Latest commit to the main branch on 3-29-2025
Download as zip