Redux 源码
let createStore = (reducer) => {
let state;
//获取状态对象
//存放所有的监听函数
let listeners = [];
let getState = () => state;
let dispach = (action) => { //提供一个方法供外部调用派发action
state = reducer(state, action); //调用管理员reducer得到新的state
listeners.forEach((listener) => {
listener() //执行所有的监听函数
})
}
let subscribe = (listener) => { // 订阅状态变化事件，当状态改变发生之后执行监听函数
listeners.push(listener);
}
dispath(); // 初始化的调用派发action函数
return {
getState,
dispath,
subscribe
}
}
let combineReducers = (reducers) => {
// 传入一个reducers管理组，返回的是一个reducer
return function(state={},action={}) {
let newState = {};
for(var attr in reducers) {
newState[attr] = reducers[attr](state[attr],action)
}
return newState;
}
}
export {createStore,combineReducers};
使用案例：
function createStore(reducer) {
var state;
var listeners = [];
var getState = () => state;
var dispatch = (action) => {
state = reducer(state, action);
listeners.forEach(lis => lis()); // 遍历执行监听函数
}
var subscribe = (listener) => {
listeners.push(listener);
return () => {
listeners = listeners.filter((lis) => { // 过滤掉当前的监听函数，避免重复订阅
return lis != listener
})
}
}
dispatch();
return {
getState, dispatch, subscribe
}
}
var reducer = (state = 0, action) => { // 输入当前状态，与行为，返回新的状态
if (!action) return state;
console.log(action);
switch (action.type) {
case 'INCREMENT':
return state + 1;
case 'DECREMENT':
return state - 1;
default:
return state;
}
}
var store = createStore(reducer);
store.subscribe(function () {
document.querySelector('#counter').innerHTML = store.getState(); // 订阅数据
});
document.querySelector('#addBtn').addEventListener('click', function () {
store.dispatch({type: 'INCREMENT'}); //分发数据
});
document.querySelector('#minusBtn').addEventListener('click', function () {
store.dispatch({type: 'DECREMENT'}); //分发数据
});
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