redux 小实现

import  {createStore} from "redux";  //引入生成store的方法
//配置reducer规则
function counter(state=0,action) {
    switch(action.type){
        case "red":
            return state+1;
        case "green":
            return state-1;
        default:
            return 10;

    }
}

//通过reducer来生成store
const store=createStore(counter);

const init =store.getState();//获取到当前的state

console.log(init);
//订阅函数
function listen(){
    var counter = store.getState();
    console.log(`now num is ${counter}`);

}
store.subscribe(listen) //设置监听函数，只要dispath 都会触发 该方法

//派发事件,生成新的state
store.dispatch({type:"red"});
store.dispatch({type:"red"});
store.dispatch({type:"green"});

//简单来说就是 dispatch替代了setState