redux

import { createSlice, PayloadAction } from '@reduxjs/toolkit';

interface CounterState {
  value: number;
}

const initialState: CounterState = { value: 0 };

const counterSlice = createSlice({
  name: 'counter',
  initialState,
  reducers: {
    increment(state) { state.value += 1; },
    decrement(state) { state.value -= 1; },
    incrementByAmount(state, action: PayloadAction<number>) {
      state.value += action.payload;
    },
  },
});

export const { increment, decrement, incrementByAmount } = counterSlice.actions;
export default counterSlice.reducer;

import { configureStore } from '@reduxjs/toolkit';
import counterReducer from './counterSlice';

export const store = configureStore({
  reducer: {
    counter: counterReducer,
  },
});

export type RootState = ReturnType<typeof store.getState>;
export type AppDispatch = typeof store.dispatch;

import { useSelector, useDispatch } from 'react-redux';
import { RootState, AppDispatch } from './store';
import { increment, decrement } from './counterSlice';

export function Counter() {
  const count = useSelector((state: RootState) => state.counter.value);
  const dispatch = useDispatch<AppDispatch>();

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => dispatch(increment())}>+</button>
      <button onClick={() => dispatch(decrement())}>-</button>
    </div>
  );
}

import { createAsyncThunk } from '@reduxjs/toolkit';

export const fetchUsers = createAsyncThunk('users/fetch', async () => {
  const response = await fetch('/api/users');
  return response.json();
});