实现vuex原理的示例

import Vue from 'vue'
import Vuex from 'vuex' 
// import Vuex from './myvuex'   //我们实现的 青铜版vuex
// import Vuex from './myvuexplus' //我们实现的 白银版vuex

Vue.use(Vuex) //执行install方法 将new Vuex.Store挂载到this.$store

export default new Vuex.Store({
 state: {
  counter: 0,
  userData: {
   name: '时间',
   age: 18
  }
 },
 getters: {
  name(state) {
   return state.userData.name
  }
 },
 mutations: {
  add(state) {
   state.counter++
  },
  updateName(state, payload) {
   state.userData.name = payload
  }
 },
 actions: {
  add({ mit }) {
   setTimeout(() => {
    mit('add')
   }, 1000);
  }
 }
})

let Vue
class Store {
 constructor(options) {
  this._vm = new Vue({
   data: {
    state: options.state
   }
  })

  let getters = options.getters
  this.getters = {}
  Object.keys(getters).forEach((val) => {
   Object.defineProperty(this.getters, val, { //getters响应式
    get: () => {
     return getters[val](this.state)
    }
   })
  })

  this._actions = Object.assign({}, options.actions)
  this._mutations = Object.assign({}, options.mutations)
 }

 // get/set state目的防止外部直接修改state
 get state() {
  return this._vm.state
 }
 set state(value) {
  console.error('please use replaceState to reset state')
 }

 mit = (funName, params) => { //this执行问题
  // 在mutations中找到funName中对应的函数并且执行
  this._mutations[funName](this.state, params)
 }

 dispatch(funName, params) {
  this._actions[funName](this, params)
 }
}

function install(vue) {
 Vue = vue
 vue.mixin({
  beforeCreate () {
   // 将 new Store() 实例挂载到唯一的根组件 this 上
   if (this.$options?.store) {
    this.$store = this.$options.store
   } else {
    this.$store = this.$parent && this.$parent.$store
   }
  }
 })
}

export default {
 Store,
 install
}

let _Vue
const install = function(Vue, opts) {
 _Vue = Vue
 _Vue.mixin({ // 因为我们每个组件都有 this.$store这个东西，所以我们使用混入模式
  beforeCreate () { // 从根组件向子组件遍历赋值，这边的 this 就是每个 Vue 实例
   if (this.$options && this.$options.store) { // 这是根节点
    this.$store = this.$options.store
   } else {
    this.$store = this.$parent && this.$parent.$store
   }
  }
 })
}

class ModuleCollection {
 constructor(opts) {
  this.root = this.register(opts)
 }

 register(module) {
  let newModule = {
   _raw: module,
   _state: module.state || {},
   _children: {}
  }
  Object.keys(module.modules || {}).forEach(moduleName => {
   newModule._children[moduleName] = this.register(module.modules[moduleName])
  })
  return newModule
 }
}

class Store {
 constructor(opts) {
  this.vm = new _Vue({
   data () {
    return {
     state: opts.state // 把对象变成响应式的，这样才能更新视图
    }
   }
  })

  this.getters = {}
  this.mutations = {}
  this.actions = {}

  // 先格式化传进来的 modules 数据
  // 嵌套模块的 mutation 和 getters 都需要放到 this 中
  this.modules = new ModuleCollection(opts)
  console.log(this.modules)

  Store.installModules(this, [], this.modules.root)
 }

 mit = (mutationName, value) => { // 这个地方 this 指向会有问题，这其实是挂载在实例上
  this.mutations[mutationName].forEach(f => f(value))
 }

 dispatch(actionName, value) {
  this.actions[actionName].forEach(f => f(value))
 }

 get state() {
  return this.vm.state
 }
}
Store.installModules = function(store, path, curModule) {
 let getters = curModule._raw.getters || {}
 let mutations = curModule._raw.mutations || {}
 let actions = curModule._raw.actions || {}
 let state = curModule._state || {}

 // 把子模块的状态挂载到父模块上，其他直接挂载到根 store 上即可
 if (path.length) {
  let parent = path.slice(0, -1).reduce((pre, cur) => {
   return pre[cur]
  }, store.state)
  _Vue.set(parent, path[path.length - 1], state)
 }

 Object.keys(getters).forEach(getterName => {
  Object.defineProperty(store.getters, getterName, {
   get: () => {
    return getters[getterName](state)
   }
  })
 })

 Object.keys(mutations).forEach(mutationName => {
  if (!(store.mutations && store.mutations[mutationName])) store.mutations[mutationName] = []
  store.mutations[mutationName].push(value => {
   mutations[mutationName].call(store, state, value)
  })
 })

 Object.keys(actions).forEach(actionName => {
  if (!(store.actions && store.actions[actionName])) store.actions[actionName] = []
  store.actions[actionName].push(value => {
   actions[actionName].call(store, store, value)
  })
 })

 Object.keys(curModule._children || {}).forEach(module => {
  Store.installModules(store, path.concat(module), curModule._children[module])
 })


}

// puted: mapState(['name'])
// 相当于 name(){ return this.$store.state.name }
const mapState = list => { // 因为要在 puted 中调用
 let obj = {}
 list.forEach(stateName => {
  obj[stateName] = () => this.$store.state[stateName]
 })
 return obj
}

const mapGetters = list => { // 因为要在 puted 中调用
 let obj = {}
 list.forEach(getterName => {
  obj[getterName] = () => this.$store.getters[getterName]
 })
 return obj
}

const mapMutations = list => {
 let obj = {}
 list.forEach(mutationName => {
  obj[mutationName] = (value) => {
   this.$store.mit(mutationName, value)
  }
 })
 return obj
}

const mapActions = list => {
 let obj = {}
 list.forEach(actionName => {
  obj[actionName] = (value) => {
   this.$store.dispatch(actionName, value)
  }
 })
 return obj
}

export default {
 install,
 Store,
 mapState,
 mapGetters,
 mapMutations,
 mapActions
}

<template>
 <div id="app">
  <button @click="$store.mit('add')">$store.mit('add'): {{$store.state.counter}}</button>
  <br>
  <button @click="$store.mit('updateName', new Date().toLocaleString())">$store.mit('updateName', Date): {{$store.getters.name}}</button>
  <br>
  <button @click="$store.dispatch('add')">async $store.dispatch('add'): {{$store.state.counter}}</button>
 </div>
</template>
<script>
...