Function useAtomValue

src/react/useAtomValue.ts:120–206

(atom: Atom<Value>, options?: Options)

): Awaited<ExtractAtomValue<AtomType>>

export function useAtomValue<Value>(atom: Atom<Value>, options?: Options) {
  const { delay, unstable_promiseStatus: promiseStatus = !React.use } =
    options || {}
  const store = useStore(options)

  const [[valueFromReducer, storeFromReducer, atomFromReducer], rerender] =
    useReducer<readonly [Value, Store, typeof atom], undefined, []>(
      (prev) => {
        const nextValue = store.get(atom)
        if (
          Object.is(prev[0], nextValue) &&
          prev[1] === store &&
          prev[2] === atom
        ) {
          return prev
        }
        return [nextValue, store, atom]
      },
      undefined,
      () => [store.get(atom), store, atom],
    )

  let value = valueFromReducer
  if (storeFromReducer !== store || atomFromReducer !== atom) {
    rerender()
    value = store.get(atom)
  }

  useEffect(() => {
    const unsub = store.sub(atom, () => {
      if (promiseStatus) {
        try {
          const value = store.get(atom)
          if (isPromiseLike(value)) {
            attachPromiseStatus(
              createContinuablePromise(store, value, () => store.get(atom)),
            )
          }
        } catch {
          // ignore
        }
      }
      if (typeof delay === 'number') {
        console.warn(`[DEPRECATED] delay option is deprecated and will be removed in v3.

Migration guide:

Create a custom hook like the following.

function useAtomValueWithDelay<Value>(
  atom: Atom<Value>,
  options: { delay: number },
): Value {
  const { delay } = options
  const store = useStore(options)
  const [value, setValue] = useState(() => store.get(atom))
  useEffect(() => {
    const unsub = store.sub(atom, () => {