React useReducer Hook

useReducer manages complex state logic better than useState.

Basic Example

import { useReducer } from 'react';

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

function Counter() {
  const [state, dispatch] = useReducer(reducer, { count: 0 });

  return (
    <div>
      <p>Count: {state.count}</p>
      <button onClick={() => dispatch({ type: 'increment' })}>+</button>
      <button onClick={() => dispatch({ type: 'decrement' })}>-</button>
    </div>
  );
}

When to Use

• Complex state logic
• Multiple sub-values
• Next state depends on previous

With Payload

function reducer(state, action) {
  switch (action.type) {
    case 'add':
      return { count: state.count + action.value };
    default:
      return state;
  }
}

dispatch({ type: 'add', value: 5 });

Next: Learn useRef hook!