The content of this article is about a simple implementation method (code) of redux. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
Introduction: Handwritten implementation of redux/react-redux basic api
redux api
createStore(reducer, [preloadedState], enhancer)
创建一个 Redux store 来以存放应用中所有的 state reducer (Function): 接收两个参数,当前的 state 树/要处理的 action,返回新的 state 树 preloadedState: 初始时的 state enhancer (Function): store creator 的高阶函数,返回一个新的强化过的 store creator
Store method
getState() 返回应用当前的 state 树 dispatch(action) 分发 action。这是触发 state 变化的惟一途径 subscribe(listener) 添加一个变化监听器。每当 dispatch action 的时候就会执行,state 树中的一部分可能已经变化 replaceReducer(nextReducer) 替换 store 当前用来计算 state 的 reducer
combineReducers(reducers)
把一个由多个不同 reducer 函数作为 value 的 object,合并成一个最终的 reducer 函数
import { combineReducers } from 'redux' import todos from './todos' import counter from './counter' export default combineReducers({ todos, counter })
applyMiddleware(...middleware)
使用包含自定义功能的 middleware 来扩展 Redux 是 ...middleware (arguments): 遵循 Redux middleware API 的函数。每个 middleware 接受 Store 的 dispatch 和 getState 函数作为命名参数,并返回一个函数。该函数会被传入 被称为 next 的下一个 middleware 的 dispatch 方法,并返回一个接收 action 的新函数,这个函数可以直接调用 next(action),或者在其他需要的时刻调用,甚至根本不去调用它。调用链中最后一个 middleware 会接受真实的 store 的 dispatch 方法作为 next 参数,并借此结束调用链。所以,middleware 的函数签名是 ({ getState, dispatch }) => next => action
import { createStore, combineReducers, applyMiddleware } from 'redux' import thunk from 'redux-thunk' import * as reducers from './reducers' let reducer = combineReducers(reducers) // applyMiddleware 为 createStore 注入了 middleware: let store = createStore(reducer, applyMiddleware(thunk))
bindActionCreators(actionCreators, dispatch)
compose(...functions)
Compose multiple combinations from right to left function.When multiple store enhancers need to be executed in sequence, you need to use it
import { createStore, applyMiddleware, compose } from 'redux' import thunk from 'redux-thunk' import DevTools from './containers/DevTools' import reducer from '../reducers' const store = createStore( reducer, compose( applyMiddleware(thunk), DevTools.instrument() ) )
Implement a simple redux
Use redux to implement
// import { createStore } from 'redux' // 将redux文件替换成自己实现的redux文件 import { createStore } from './self-redux.js' // 这就是reducer处理函数,参数是状态和新的action function counter(state=0, action) { // let state = state||0 switch (action.type) { case '加机关枪': return state + 1 case '减机关枪': return state - 1 default: return 10 } } // 新建store const store = createStore(counter) const init = store.getState() console.log(`一开始有机枪${init}把`) function listener(){ const current = store.getState() console.log(`现在有机枪${current}把`) } // 订阅,每次state修改,都会执行listener store.subscribe(listener) // 提交状态变更的申请 store.dispatch({ type: '加机关枪' })
Implement createStore, store related methods
./self-redux.js export function createStore(reducer) { let currentState = {} let currentListeners = [] function getState() { return currentState } function subscribe(listeners) { currentListeners.push(listener) } function dispatch(action) { currentState = reducer(currentState, action) currentListeners.forEach(v => v()) return action } dispatch({ type: '@rainie/init-store' }) return { getState, subscribe, dispatch } }
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