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jotai is a state management library for React applications that offers a simple and flexible way to manage state using atoms and selectors. It provides a lightweight and scalable solution for handling state in React components. While jotai is a powerful state management library, there are other alternatives available in the React ecosystem. Here are a few alternatives:

• mobx is a popular state management library that enables reactive programming in JavaScript. It provides observables and reactions to manage state in an efficient and reactive manner.
• recoil is a state management library developed by Facebook that focuses on providing a more declarative approach to managing state in React applications. It offers features like atoms and selectors for managing state.
• redux is a widely-used state management library for React applications. It follows a unidirectional data flow pattern and uses a single immutable state tree to manage the application's state.
• zustand is a minimalistic state management library that aims to simplify state management in React applications. It provides a simple API for creating and updating state.

Check out this comparison: Comparing jotai vs mobx vs recoil vs redux vs zustand.

visit jotai.org or npm i jotai

Jotai scales from a simple useState replacement to an enterprise TypeScript application.

• Minimal core API (2kb)
• Many utilities and extensions
• No string keys (compared to Recoil)

Examples: Demo 1 | Demo 2

First, create a primitive atom

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 })

Use the atom in your components

It can be used 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>
      ...

Create derived atoms with computed values

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>
}

Creating an atom from multiple atoms

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))

Or if you like fp patterns ...

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

Derived async atoms

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 is changed and the async function above concludes
  const [json] = useAtom(fetchUrlAtom)
  ...

You can create a writable derived atom

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

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>
      ...

Write only derived atoms

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>
}

Async actions

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>
    ...

Links

• website
• documentation
• course