50行代码 实现Redux 核心功能
Redux 帮助你管理“全局”状态 - 那些应用程序的许多部分都需要的状态
redux的核心就是对数据状态进行管理，创建一个数据仓库
Redux顺序分四大步：
- 初始化
- 订阅
- 发布
- 执行匹配和更新
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Redux</title>
</head>
<body>
<button id="addto">加1</button>
</body>
<script>
// 创建全局变量
window.Redux = {};
function createStore(reducer) {
// state 是存储在store中的数据
let state;
let listeners = [];
// 获取最新的state仓库内容
function getState() {
return state
};
// 订阅，发布
function subscribe(callback) {
listeners.push(callback)
};
// reducer 修改state，接收参数action
function dispatch(action) {
// 更新仓库
state = reducer(state, action);
// 循环执行订阅过的subscribe函数回调
for (let i = 0; i < listeners.length; i++) {
let listener = listeners[i]
listener()
}
};
// 在store初始化的时候需要执行一次reducer
state = reducer(state, {
type: '@@init/redux.x.x.x'
});
let store = {
getState,
subscribe,
dispatch
};
return store;
};
Redux.createStore = createStore;
const initState = {
milk: 0
};
// 执行 action 对应的type更新 state仓库
function reducer(state = initState, action) {
switch (action.type) {
case 'PUTMILK':
return {
...state, milk: state.milk + action.count
}
case 'TAKE_MILK':
return {
...state, milk: state.milk - action.count
}
case '@@init/redux.x.x.x':
return { ...state }
default:
return state
}
};
// redux 的使用
// 初始化
let store = createStore(reducer);
// 订阅，只要state发生改变 就会通知订阅者
store.subscribe(() => console.log('仓库更新了',store.getState()));
// 发布-执行
store.dispatch({
type: 'PUTMILK',
count: 1
});
let dom = document.getElementById("addto");
dom.onclick = () => {
store.dispatch({
type: 'PUTMILK',
count: 1
});
console.log(store.getState())
};
</script>
</html>
