基本

import { createStore } from 'redux';

// reducer 是个函数，参数为 state（设置初始值）和 action,返回值为新的 state
const reducer = (state = 0, action){
    switch (action.type) {
        case 'add':
            return state + action.payload;
        case 'delete':
            return state - action.payload;
        default:
            return state;
    }
}

// 生成 store
let store = createStore(reducer);

// 获取状态
store.getState();

const action1 = {
    type: 'add',
    payload: 2,
}

// action 生成函数
const createAction = (val) => ({
    type: 'add',
    payload: val,
})

// 使用 store.dispatch(action)来分发 action
store.dispatch(action1);
store.dispatch(createAction(2));

//store 还可以订阅监听器
// 当我们 dispatch 了 action 后，会触发函数
store.subscribe(() => {
    console.log('change state');
})