/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 vote138 views1 answer
React native run real device
Javascript React
0 vote128 views1 answer
Switch React Native Paper
Javascript React
0 vote136 views1 answer
Reactjs Developer
Javascript React
2 votes140 views2 answers
Update specific properties of an object react spread operator
Javascript React
0 vote148 views1 answer
Library to add navigation in react native
Javascript React
50 votes135 views6 answers
Yarn create react app
Javascript React
0 vote147 views1 answer
Semantic UI react focus on input
Javascript React
93 votes142 views6 answers
React router dom install
Javascript React
-1 vote153 views2 answers
React native Platform
Javascript React
1 vote106 views2 answers
How to not use relative imports in react js
Javascript React