/Javascript/React/What does the useReducer do in react

What does the useReducer do in react

UseReducer

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>
    </>
  );
}

Source: reactjs.org

UseReducer

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 (
    <>
      Count: {state.count}
      <button
        onClick={() => dispatch({type: 'reset', payload: initialCount})}>        Reset
      </button>
      <button onClick={() => dispatch({type: 'decrement'})}>-</button>
      <button onClick={() => dispatch({type: 'increment'})}>+</button>
    </>
  );
}

Source: reactjs.org

What does the useReducer do in react

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

Source: css-tricks.com

Similar codes

4 votes447 views1 answer
Full width of image and maintain aspect ratio react native
Javascript React
8 votes347 views4 answers
Props react
Javascript React
0 vote402 views3 answers
React-native restart app
Javascript React
4 votes388 views2 answers
React countdown timer
Javascript React
0 vote392 views1 answer
React form hook trigger is not a function
Javascript React
0 vote387 views1 answer
Exemple de modal reactjs
Javascript React
0 vote393 views1 answer
React-navigation headerbackbutton not export member of navigation
Javascript React
-2 votes439 views1 answer
Fc in react
Javascript React
1 vote394 views1 answer
Reactjs get checkbox value
Javascript React
2 votes422 views2 answers
React native asign width to image
Javascript React