React useReducer: Complex State Logic Made Simple

useReducer is useState’s more powerful sibling. When state logic gets complex, useReducer brings predictability.

Basic Usage

const initialState = { count: 0 };

function reducer(state, action) {
  switch (action.type) {
    case 'increment': return { count: state.count + 1 };
    case 'decrement': return { count: state.count - 1 };
    case 'reset': return initialState;
    default: throw new Error();
  }
}

function Counter() {
  const [state, dispatch] = useReducer(reducer, initialState);
  
  return (
    <div>
      Count: {state.count}
      <button onClick={() => dispatch({ type: 'increment' })}>+</button>
      <button onClick={() => dispatch({ type: 'decrement' })}>-</button>
      <button onClick={() => dispatch({ type: 'reset' })}>Reset</button>
    </div>
  );
}

With Context

Combine useReducer with Context for app-wide state management – a simpler alternative to Redux:

const StateContext = createContext();
const DispatchContext = createContext();

function AppProvider({ children }) {
  const [state, dispatch] = useReducer(reducer, initialState);
  return (
    <StateContext.Provider value={state}>
      <DispatchContext.Provider value={dispatch}>
        {children}
      </DispatchContext.Provider>
    </StateContext.Provider>
  );
}

When to Use useReducer

• Multiple related state updates
• Next state depends on previous state
• Complex state objects
• Want Redux-like patterns without Redux