Primitive and flexible state management for React




import { atom, useAtom } from 'jotai'
import { useHydrateAtoms } from 'jotai/utils'
const countAtom = atom(0)
const CounterPage = ({ countFromServer }) => {
useHydrateAtoms([[countAtom, countFromServer]])
const [count] = useAtom(countAtom)
// count would be the value of `countFromServer`, not 0.

The primary use case for useHydrateAtoms are SSR apps like Next.js, where an initial value is e.g. fetched on the server, which can be passed to a component by props.

// Definition
function useHydrateAtoms(values: Iterable<readonly [Atom<unknown>, unknown]>, scope?: Scope): void

The hook takes an iterable of tuples containing [atom, value] as an argument and optionally scope.

// Usage with an array, specifying a scope
useHydrateAtoms([[countAtom, 42], [frameworkAtom, "Next.js"]], myScope)
// Or with a map
const [initialValues] = useState(() => new Map([[count, 42]]))

Atoms can only be hydrated once per scope. Therefore, if the initial value used is changed during rerenders, it won't update the atom value.

If there's a need to hydrate in multiple scopes, use multiple useHydrateAtoms hooks to achieve that.

useHydrateAtoms([[countAtom, 42], [frameworkAtom, "Next.js"]])
useHydrateAtoms([[countAtom, 17], [frameworkAtom, "Gatsby"]], myScope)


There's more examples in the Next.js section.