/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

0 vote210 views1 answer
`ForwardRef(ListboxComponent)`, expected a ReactNode. at ListboxComponent
Javascript React
2 votes183 views1 answer
React add gradient top to bottom
Javascript React
29 votes200 views6 answers
React background image
Javascript React
2 votes197 views2 answers
React native position absolute center
Javascript React
0 vote183 views1 answer
String contains in react
Javascript React
4 votes215 views1 answer
Use of useNavigate from 'react-router-dom'
Javascript React
3 votes200 views4 answers
React Redux Thunk
Javascript React
3 votes197 views2 answers
Link react
Javascript React
0 vote190 views1 answer
Scirpt tag react
Javascript React
1 vote233 views5 answers
Enzyme adapter react 17
Javascript React