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Answers for "reducer react"

Javascript
12

reducer in react example

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>
    </>
  );
}
Posted by: Guest on June-21-2020
1

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>
    </>
  );
}
Posted by: Guest on June-21-2020
0

react/redux reducers sintaxe

const reduxSinaxe = (state = [], action) => {
  switch (action.type) {
    case "@smthg/ACTION":
      const { anyConst } = action;
      return [...state, anyConst];

    default:
      return state;
  }
};

export default reduxSinaxe;
Posted by: Guest on December-02-2020
0

reducer react

const getTotalItems = (items: CartItemType[]) =>
    items.reduce((ack: number, item) => ack + item.amount, 0);
Posted by: Guest on September-06-2021

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