/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 vote312 views1 answer
React conditional if localhost
Javascript React
0 vote321 views6 answers
State functions of react cheatsheet
Javascript React
1 vote354 views1 answer
React event target square brackets
Javascript React
-1 vote317 views4 answers
React tutorial
Javascript React
0 vote337 views1 answer
Icon button react
Javascript React
0 vote342 views1 answer
Formatt json to create node and child node react
Javascript React
6 votes376 views3 answers
Apply required attribute on input using ternary operator using react js
Javascript React
2 votes318 views2 answers
React aws s3 npm
Javascript React
1 vote381 views1 answer
Remove underline from hyperlink react
Javascript React
112 votes374 views6 answers
Import bootstrap 4 in react
Javascript React