Scope

There are a few libraries to extend Jotai's usage in React.

jotai-scope

While Jotai's Provider allows to scope Jotai's store under a subtree, we can't use the store above the tree within the subtree.

A workaround is to use store option in useAtom and other hooks. To ease such use cases, jotai-scope provides a scoped provider and hooks. Instead of specifying the store option, the scoped provider accepts atoms prop and the use of those atoms is scoped within the subtree.

Install

npm install jotai-scope

Counter Example

import { atom, useAtom } from 'jotai'
import { ScopeProvider } from 'jotai-scope'

const countAtom = atom(0)
const anotherCountAtom = atom(0)

const Counter = () => {
  const [count, setCount] = useAtom(countAtom)
  const [anotherCount, setAnotherCount] = useAtom(anotherCountAtom)
  return (
    <>
      <div>
        <span>count: {count}</span>
        <button type="button" onClick={() => setCount((c) => c + 1)}>
          increment
        </button>
      </div>
      <div>
        <span>another count: {anotherCount}</span>
        <button type="button" onClick={() => setAnotherCount((c) => c + 1)}>
          increment
        </button>
      </div>
    </>
  )
}

const App = () => {
  return (
    <div>
      <h1>First Provider</h1>
      <ScopeProvider atoms={[anotherCountAtom]}>
        <Counter />
      </ScopeProvider>
      <h1>Second Provider</h1>
      <ScopeProvider atoms={[anotherCountAtom]}>
        <Counter />
      </ScopeProvider>
    </div>
  )
}

createIsolation

Both Jotai's Provider and jotai-scope's scoped provider are still using global contexts.

If you are developing a library that depends on Jotai and the library user may use Jotai separately in their apps, they can share the same context. This can be troublesome because they point to unexpected Jotai stores.

To avoid conflicting the contexts, a utility function called createIsolation is exported from jotai-scope.

Check out the example in the repo: https://github.com/jotaijs/jotai-scope/tree/main/examples/01_isolation

bunshi (formerly jotai-molecules)

Jotai atoms provide a basic solution to optimize re-renders. Atoms defined globally can depend on other atoms, but they can't depend on props and state within a component tree. It's possible to define atoms within a component tree, but then you would need to pass those atoms in some ways (for example, atoms-in-atom.)

bunshi is a third-party library to help such use cases.

See Motivation for more details.

Install

npm install bunshi

Counter Example

import { atom, useAtom } from 'jotai'
import { molecule, useMolecule, createScope, ScopeProvider } from 'bunshi/react'

const InitialCountScope = createScope(0)
const countMolecule = molecule((getMol, getScope) => {
  const initialCont = getScope(InitialCountScope)
  return atom(initialCont)
})

const Counter = () => {
  const countAtom = useMolecule(countMolecule)
  const [count, setCount] = useAtom(countAtom)
  return (
    <div>
      {count} <button onClick={() => setCount((c) => c + 1)}>+1</button>
    </div>
  )
}

const App = () => (
  <div>
    <h1>With initial value 1</h1>
    <ScopeProvider scope={InitialCountScope} value={1}>
      <Counter />
      <Counter />
    </ScopeProvider>
    <h1>With initial value 2</h1>
    <ScopeProvider scope={InitialCountScope} value={2}>
      <Counter />
      <Counter />
    </ScopeProvider>
    <h1>Default</h1>
    <Counter />
    <Counter />
  </div>
)