---title: useReduerAtomnav: 8.11keywords: reducer, hook, useReducerAtom---
`useReducerAtom` is a custom hook to apply a reducer to a primitive atom.
It's useful to change the update behavior temporarily.Also, consider [atomWithReducer](../utilities/reducer.mdx)for the atom-level solution.
```tsimport { useCallback } from 'react'import { useAtom } from 'jotai'import type { PrimitiveAtom } from 'jotai'
export function useReducerAtom<Value, Action>( anAtom: PrimitiveAtom<Value>, reducer: (v: Value, a: Action) => Value,) { const [state, setState] = useAtom(anAtom) const dispatch = useCallback( (action: Action) => setState((prev) => reducer(prev, action)), [setState, reducer], ) return [state, dispatch] as const}```
### Example Usage
```jsximport { atom } from 'jotai'
const countReducer = (prev, action) => { if (action.type === 'inc') return prev + 1 if (action.type === 'dec') return prev - 1 throw new Error('unknown action type')}
const countAtom = atom(0)
const Counter = () => { const [count, dispatch] = useReducerAtom(countAtom, countReducer) return ( <div> {count} <button onClick={() => dispatch({ type: 'inc' })}>+1</button> <button onClick={() => dispatch({ type: 'dec' })}>-1</button> </div> )}```
<CodeSandbox id="eg0mw" />