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---title: atomWithReducer---
Ref: https://github.com/pmndrs/jotai/issues/38
```jsimport { atomWithReducer } from 'jotai/utils'
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 countReducerAtom = atomWithReducer(0, countReducer)```
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