“Redux Reducer Пример” Ответ

REDUCER в примере React

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>
    </>
  );
}
Dangerous Dunlin

Redux Reducer

const reducer = (state = initialState, action) => {
  switch (action.type) {
    case "BUY_CAKE":
      return {
        numOfCakes: state.numOfCakes - 1,
      };
    default:
      return state;
  }
};
Omatsola Eyeoyibo

Redux Reducer Пример

import * as ActionTypes from './ActionTypes';

export const comments = (state = { errMess: null, comments: []}, action) => {
    switch (action.type) {
        case ActionTypes.ADD_COMMENTS:
            return {...state, errMess: null, comments: action.payload};

        case ActionTypes.COMMENTS_FAILED:
            return {...state, errMess: action.payload};

        default:
            return state;
    }
};
Helpless Hummingbird

Как работает Reducer в Redux

const initialState = { value: 0 }

function counterReducer(state = initialState, action) {
  // Check to see if the reducer cares about this action
  if (action.type === 'counter/increment') {
    // If so, make a copy of `state`
    return {
      ...state,
      // and update the copy with the new value
      value: state.value + 1
    }
  }
  // otherwise return the existing state unchanged
  return state
}
Moscode

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