jotai
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    1.3.5 • Public • Published

    jotai

    Primitive and flexible state management for React

    npm i jotai

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

    You can try live demos in the following: Demo 1 | Demo 2.

    How does Jotai differ from Recoil?

    • Minimalistic API
    • No string keys
    • TypeScript oriented

    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>

    Recipes

    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 needs suspense

    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)

    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 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>

    Write only 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 needs suspense

    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>

    Installation notes

    This package requires some peer dependencies, which you need to install by yourself.

    yarn add jotai react

    More documents

    Install

    npm i jotai

    Version

    1.3.5

    License

    MIT

    Unpacked Size

    431 kB

    Total Files

    266

    Last publish

    Collaborators

    • daishi
    • drcmda