/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 vote130 views1 answer
React axios get cookie from response
Javascript React
0 vote125 views1 answer
React live chat widget
Javascript React
0 vote138 views3 answers
Flatlist react native keyextractor
Javascript React
0 vote128 views3 answers
Image border shadow react native
Javascript React
0 vote136 views3 answers
React native navigation change header title
Javascript React
4 votes127 views1 answer
Error Invalid regular expression: /(.*\\__fixtures__\\.*|node_modules[\\\]react[\\\]dist[\\\].*|website\\node_modules\\.*|heapCapture\\bundle\.js|.*\\__tests__\\.*)$/: Unterminated character class.
Javascript React
23 votes138 views5 answers
USE ICONS IN REACT
Javascript React
0 vote125 views1 answer
Build class component react
Javascript React
0 vote80 views1 answer
Liquid indicators in react native
Javascript React
0 vote132 views2 answers
React firebase hooks
Javascript React