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what does the useReducer do in react

Gonja 
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};
    default:
      throw new Error();
  }
}

function Counter() {
  const [state, dispatch] = useReducer(reducer, initialState);
  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({type: 'decrement'})}>-</button>
      <button onClick={() => dispatch({type: 'increment'})}>+</button>
    </>
  );
}
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4.2
10
Walkytalky 85 points 

                                    const [state, dispatch] = useReducer(reducer, initialArg, init);

4.2 (10 Votes)
0
3.25
4
Delia Lane 85 points 

                                    const [state, dispatch] = useReducer(reducer, initialState);

3.25 (4 Votes)
0
4.43
7
Sharyn 80 points 

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

function Counter({initialCount}) {
  const [state, dispatch] = useReducer(reducer, initialCount, init);  return (
    &lt;&gt;
      Count: {state.count}
      &lt;button
        onClick={() =&gt; dispatch({type: 'reset', payload: initialCount})}&gt;        Reset
      &lt;/button&gt;
      &lt;button onClick={() =&gt; dispatch({type: 'decrement'})}&gt;-&lt;/button&gt;
      &lt;button onClick={() =&gt; dispatch({type: 'increment'})}&gt;+&lt;/button&gt;
    &lt;/&gt;
  );
}

4.43 (7 Votes)
0
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