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src/index.js

vuex的目录结构非常简单，打开src文件夹，肯定先看index.js文件

js
import { Store, createStore } from './store'
import { storeKey, useStore } from './injectKey'
import { mapState, mapMutations, mapGetters, mapActions, createNamespacedHelpers } from './helpers'
import { createLogger } from './plugins/logger'

export default {
  version: '__VERSION__',
  Store,
  storeKey,
  createStore,
  useStore,
  mapState,
  mapMutations,
  mapGetters,
  mapActions,
  createNamespacedHelpers,
  createLogger
}

export {
  Store,
  storeKey,
  createStore,
  useStore,
  mapState,
  mapMutations,
  mapGetters,
  mapActions,
  createNamespacedHelpers,
  createLogger
}

import { Store, createStore } from './store'
import { storeKey, useStore } from './injectKey'
import { mapState, mapMutations, mapGetters, mapActions, createNamespacedHelpers } from './helpers'
import { createLogger } from './plugins/logger'

export default {
  version: '__VERSION__',
  Store,
  storeKey,
  createStore,
  useStore,
  mapState,
  mapMutations,
  mapGetters,
  mapActions,
  createNamespacedHelpers,
  createLogger
}

export {
  Store,
  storeKey,
  createStore,
  useStore,
  mapState,
  mapMutations,
  mapGetters,
  mapActions,
  createNamespacedHelpers,
  createLogger
}

createStore

打开src\store.js，首先看到的是createStore函数，createStore函数是vue3中使用vuex的语法，可以看出来其实它就是new了一个Store

js
export function createStore (options) {
  return new Store(options)
}

export function createStore (options) {
  return new Store(options)
}

再往下看，Store是vuex的核心类，总共也就两百多行，一行一行看也很快

js
export class Store {
  constructor (options = {}) {
    if (__DEV__) {
      assert(typeof Promise !== 'undefined', `vuex requires a Promise polyfill in this browser.`)
      assert(this instanceof Store, `store must be called with the new operator.`)
    }

    const {
      plugins = [],
      strict = false,
      devtools
    } = options

    // store internal state
    this._committing = false
    this._actions = Object.create(null)
    this._actionSubscribers = []
    this._mutations = Object.create(null)
    this._wrappedGetters = Object.create(null)
    this._modules = new ModuleCollection(options)
    this._modulesNamespaceMap = Object.create(null)
    this._subscribers = []
    this._makeLocalGettersCache = Object.create(null)

    // EffectScope instance. when registering new getters, we wrap them inside
    // EffectScope so that getters (computed) would not be destroyed on
    // component unmount.
    this._scope = null

    this._devtools = devtools

    // bind commit and dispatch to self
    const store = this
    const { dispatch, commit } = this
    this.dispatch = function boundDispatch (type, payload) {
      return dispatch.call(store, type, payload)
    }
    this.commit = function boundCommit (type, payload, options) {
      return commit.call(store, type, payload, options)
    }

    // strict mode
    this.strict = strict

    const state = this._modules.root.state

    // init root module.
    // this also recursively registers all sub-modules
    // and collects all module getters inside this._wrappedGetters
    installModule(this, state, [], this._modules.root)

    // initialize the store state, which is responsible for the reactivity
    // (also registers _wrappedGetters as computed properties)
    resetStoreState(this, state)

    // apply plugins
    plugins.forEach(plugin => plugin(this))
  }

  install (app, injectKey) {
    app.provide(injectKey || storeKey, this)
    app.config.globalProperties.$store = this

    const useDevtools = this._devtools !== undefined
      ? this._devtools
      : __DEV__ || __VUE_PROD_DEVTOOLS__

    if (useDevtools) {
      addDevtools(app, this)
    }
  }

  get state () {
    return this._state.data
  }

  set state (v) {
    if (__DEV__) {
      assert(false, `use store.replaceState() to explicit replace store state.`)
    }
  }

  commit (_type, _payload, _options) {
    // check object-style commit
    const {
      type,
      payload,
      options
    } = unifyObjectStyle(_type, _payload, _options)

    const mutation = { type, payload }
    const entry = this._mutations[type]
    if (!entry) {
      if (__DEV__) {
        console.error(`[vuex] unknown mutation type: ${type}`)
      }
      return
    }
    this._withCommit(() => {
      entry.forEach(function commitIterator (handler) {
        handler(payload)
      })
    })

    this._subscribers
      .slice() // shallow copy to prevent iterator invalidation if subscriber synchronously calls unsubscribe
      .forEach(sub => sub(mutation, this.state))

    if (
      __DEV__ &&
      options && options.silent
    ) {
      console.warn(
        `[vuex] mutation type: ${type}. Silent option has been removed. ` +
        'Use the filter functionality in the vue-devtools'
      )
    }
  }

  dispatch (_type, _payload) {
    // check object-style dispatch
    const {
      type,
      payload
    } = unifyObjectStyle(_type, _payload)

    const action = { type, payload }
    const entry = this._actions[type]
    if (!entry) {
      if (__DEV__) {
        console.error(`[vuex] unknown action type: ${type}`)
      }
      return
    }

    try {
      this._actionSubscribers
        .slice() // shallow copy to prevent iterator invalidation if subscriber synchronously calls unsubscribe
        .filter(sub => sub.before)
        .forEach(sub => sub.before(action, this.state))
    } catch (e) {
      if (__DEV__) {
        console.warn(`[vuex] error in before action subscribers: `)
        console.error(e)
      }
    }

    const result = entry.length > 1
      ? Promise.all(entry.map(handler => handler(payload)))
      : entry[0](payload)

    return new Promise((resolve, reject) => {
      result.then(res => {
        try {
          this._actionSubscribers
            .filter(sub => sub.after)
            .forEach(sub => sub.after(action, this.state))
        } catch (e) {
          if (__DEV__) {
            console.warn(`[vuex] error in after action subscribers: `)
            console.error(e)
          }
        }
        resolve(res)
      }, error => {
        try {
          this._actionSubscribers
            .filter(sub => sub.error)
            .forEach(sub => sub.error(action, this.state, error))
        } catch (e) {
          if (__DEV__) {
            console.warn(`[vuex] error in error action subscribers: `)
            console.error(e)
          }
        }
        reject(error)
      })
    })
  }

  subscribe (fn, options) {
    return genericSubscribe(fn, this._subscribers, options)
  }

  subscribeAction (fn, options) {
    const subs = typeof fn === 'function' ? { before: fn } : fn
    return genericSubscribe(subs, this._actionSubscribers, options)
  }

  watch (getter, cb, options) {
    if (__DEV__) {
      assert(typeof getter === 'function', `store.watch only accepts a function.`)
    }
    return watch(() => getter(this.state, this.getters), cb, Object.assign({}, options))
  }

  replaceState (state) {
    this._withCommit(() => {
      this._state.data = state
    })
  }

  registerModule (path, rawModule, options = {}) {
    if (typeof path === 'string') path = [path]

    if (__DEV__) {
      assert(Array.isArray(path), `module path must be a string or an Array.`)
      assert(path.length > 0, 'cannot register the root module by using registerModule.')
    }

    this._modules.register(path, rawModule)
    installModule(this, this.state, path, this._modules.get(path), options.preserveState)
    // reset store to update getters...
    resetStoreState(this, this.state)
  }

  unregisterModule (path) {
    if (typeof path === 'string') path = [path]

    if (__DEV__) {
      assert(Array.isArray(path), `module path must be a string or an Array.`)
    }

    this._modules.unregister(path)
    this._withCommit(() => {
      const parentState = getNestedState(this.state, path.slice(0, -1))
      delete parentState[path[path.length - 1]]
    })
    resetStore(this)
  }

  hasModule (path) {
    if (typeof path === 'string') path = [path]

    if (__DEV__) {
      assert(Array.isArray(path), `module path must be a string or an Array.`)
    }

    return this._modules.isRegistered(path)
  }

  hotUpdate (newOptions) {
    this._modules.update(newOptions)
    resetStore(this, true)
  }

  _withCommit (fn) {
    const committing = this._committing
    this._committing = true
    fn()
    this._committing = committing
  }
}

export class Store {
  constructor (options = {}) {
    if (__DEV__) {
      assert(typeof Promise !== 'undefined', `vuex requires a Promise polyfill in this browser.`)
      assert(this instanceof Store, `store must be called with the new operator.`)
    }

    const {
      plugins = [],
      strict = false,
      devtools
    } = options

    // store internal state
    this._committing = false
    this._actions = Object.create(null)
    this._actionSubscribers = []
    this._mutations = Object.create(null)
    this._wrappedGetters = Object.create(null)
    this._modules = new ModuleCollection(options)
    this._modulesNamespaceMap = Object.create(null)
    this._subscribers = []
    this._makeLocalGettersCache = Object.create(null)

    // EffectScope instance. when registering new getters, we wrap them inside
    // EffectScope so that getters (computed) would not be destroyed on
    // component unmount.
    this._scope = null

    this._devtools = devtools

    // bind commit and dispatch to self
    const store = this
    const { dispatch, commit } = this
    this.dispatch = function boundDispatch (type, payload) {
      return dispatch.call(store, type, payload)
    }
    this.commit = function boundCommit (type, payload, options) {
      return commit.call(store, type, payload, options)
    }

    // strict mode
    this.strict = strict

    const state = this._modules.root.state

    // init root module.
    // this also recursively registers all sub-modules
    // and collects all module getters inside this._wrappedGetters
    installModule(this, state, [], this._modules.root)

    // initialize the store state, which is responsible for the reactivity
    // (also registers _wrappedGetters as computed properties)
    resetStoreState(this, state)

    // apply plugins
    plugins.forEach(plugin => plugin(this))
  }

  install (app, injectKey) {
    app.provide(injectKey || storeKey, this)
    app.config.globalProperties.$store = this

    const useDevtools = this._devtools !== undefined
      ? this._devtools
      : __DEV__ || __VUE_PROD_DEVTOOLS__

    if (useDevtools) {
      addDevtools(app, this)
    }
  }

  get state () {
    return this._state.data
  }

  set state (v) {
    if (__DEV__) {
      assert(false, `use store.replaceState() to explicit replace store state.`)
    }
  }

  commit (_type, _payload, _options) {
    // check object-style commit
    const {
      type,
      payload,
      options
    } = unifyObjectStyle(_type, _payload, _options)

    const mutation = { type, payload }
    const entry = this._mutations[type]
    if (!entry) {
      if (__DEV__) {
        console.error(`[vuex] unknown mutation type: ${type}`)
      }
      return
    }
    this._withCommit(() => {
      entry.forEach(function commitIterator (handler) {
        handler(payload)
      })
    })

    this._subscribers
      .slice() // shallow copy to prevent iterator invalidation if subscriber synchronously calls unsubscribe
      .forEach(sub => sub(mutation, this.state))

    if (
      __DEV__ &&
      options && options.silent
    ) {
      console.warn(
        `[vuex] mutation type: ${type}. Silent option has been removed. ` +
        'Use the filter functionality in the vue-devtools'
      )
    }
  }

  dispatch (_type, _payload) {
    // check object-style dispatch
    const {
      type,
      payload
    } = unifyObjectStyle(_type, _payload)

    const action = { type, payload }
    const entry = this._actions[type]
    if (!entry) {
      if (__DEV__) {
        console.error(`[vuex] unknown action type: ${type}`)
      }
      return
    }

    try {
      this._actionSubscribers
        .slice() // shallow copy to prevent iterator invalidation if subscriber synchronously calls unsubscribe
        .filter(sub => sub.before)
        .forEach(sub => sub.before(action, this.state))
    } catch (e) {
      if (__DEV__) {
        console.warn(`[vuex] error in before action subscribers: `)
        console.error(e)
      }
    }

    const result = entry.length > 1
      ? Promise.all(entry.map(handler => handler(payload)))
      : entry[0](payload)

    return new Promise((resolve, reject) => {
      result.then(res => {
        try {
          this._actionSubscribers
            .filter(sub => sub.after)
            .forEach(sub => sub.after(action, this.state))
        } catch (e) {
          if (__DEV__) {
            console.warn(`[vuex] error in after action subscribers: `)
            console.error(e)
          }
        }
        resolve(res)
      }, error => {
        try {
          this._actionSubscribers
            .filter(sub => sub.error)
            .forEach(sub => sub.error(action, this.state, error))
        } catch (e) {
          if (__DEV__) {
            console.warn(`[vuex] error in error action subscribers: `)
            console.error(e)
          }
        }
        reject(error)
      })
    })
  }

  subscribe (fn, options) {
    return genericSubscribe(fn, this._subscribers, options)
  }

  subscribeAction (fn, options) {
    const subs = typeof fn === 'function' ? { before: fn } : fn
    return genericSubscribe(subs, this._actionSubscribers, options)
  }

  watch (getter, cb, options) {
    if (__DEV__) {
      assert(typeof getter === 'function', `store.watch only accepts a function.`)
    }
    return watch(() => getter(this.state, this.getters), cb, Object.assign({}, options))
  }

  replaceState (state) {
    this._withCommit(() => {
      this._state.data = state
    })
  }

  registerModule (path, rawModule, options = {}) {
    if (typeof path === 'string') path = [path]

    if (__DEV__) {
      assert(Array.isArray(path), `module path must be a string or an Array.`)
      assert(path.length > 0, 'cannot register the root module by using registerModule.')
    }

    this._modules.register(path, rawModule)
    installModule(this, this.state, path, this._modules.get(path), options.preserveState)
    // reset store to update getters...
    resetStoreState(this, this.state)
  }

  unregisterModule (path) {
    if (typeof path === 'string') path = [path]

    if (__DEV__) {
      assert(Array.isArray(path), `module path must be a string or an Array.`)
    }

    this._modules.unregister(path)
    this._withCommit(() => {
      const parentState = getNestedState(this.state, path.slice(0, -1))
      delete parentState[path[path.length - 1]]
    })
    resetStore(this)
  }

  hasModule (path) {
    if (typeof path === 'string') path = [path]

    if (__DEV__) {
      assert(Array.isArray(path), `module path must be a string or an Array.`)
    }

    return this._modules.isRegistered(path)
  }

  hotUpdate (newOptions) {
    this._modules.update(newOptions)
    resetStore(this, true)
  }

  _withCommit (fn) {
    const committing = this._committing
    this._committing = true
    fn()
    this._committing = committing
  }
}

useStore

打开src\injectKey.js，看看useStore如何实现的，可以看到代码非常简单，不传入key的话，就默认injectstore这个key值

provide 和 inject 是vue依赖注入机制的语法。一个父组件使用provide提供依赖，其所有的后代组件，无论层级有多深，都可以inject获取由父组件provide提供的依赖

依赖注入 https://cn.vuejs.org/guide/components/provide-inject.html

js
import { inject } from 'vue'

export const storeKey = 'store'

export function useStore (key = null) {
  return inject(key !== null ? key : storeKey)
}

import { inject } from 'vue'

export const storeKey = 'store'

export function useStore (key = null) {
  return inject(key !== null ? key : storeKey)
}

有inject说明有provide，他就在上面的src\store.js代码中，install函数第一行就provide了store

js
 install (app, injectKey) {
    app.provide(injectKey || storeKey, this)
    ...
  }

 install (app, injectKey) {
    app.provide(injectKey || storeKey, this)
    ...
  }

mapState

打开src\helpers.js，看看辅助函数们是怎么实现的

js
/**
 * Reduce the code which written in Vue.js for getting the state.
 * @param {String} [namespace] - Module's namespace
 * @param {Object|Array} states # Object's item can be a function which accept state and getters for param, you can do something for state and getters in it.
 * @param {Object}
 */
export const mapState = normalizeNamespace((namespace, states) => {
  const res = {}
  if (__DEV__ && !isValidMap(states)) {
    console.error("[vuex] mapState: mapper parameter must be either an Array or an Object")
  }
  normalizeMap(states).forEach(({ key, val }) => {
    res[key] = function mappedState() {
      let state = this.$store.state
      let getters = this.$store.getters
      if (namespace) {
        const module = getModuleByNamespace(this.$store, "mapState", namespace)
        if (!module) {
          return
        }
        state = module.context.state
        getters = module.context.getters
      }
      return typeof val === "function" ? val.call(this, state, getters) : state[val]
    }
    // mark vuex getter for devtools
    res[key].vuex = true
  })
  return res
})

/**
 * Reduce the code which written in Vue.js for getting the state.
 * @param {String} [namespace] - Module's namespace
 * @param {Object|Array} states # Object's item can be a function which accept state and getters for param, you can do something for state and getters in it.
 * @param {Object}
 */
export const mapState = normalizeNamespace((namespace, states) => {
  const res = {}
  if (__DEV__ && !isValidMap(states)) {
    console.error("[vuex] mapState: mapper parameter must be either an Array or an Object")
  }
  normalizeMap(states).forEach(({ key, val }) => {
    res[key] = function mappedState() {
      let state = this.$store.state
      let getters = this.$store.getters
      if (namespace) {
        const module = getModuleByNamespace(this.$store, "mapState", namespace)
        if (!module) {
          return
        }
        state = module.context.state
        getters = module.context.getters
      }
      return typeof val === "function" ? val.call(this, state, getters) : state[val]
    }
    // mark vuex getter for devtools
    res[key].vuex = true
  })
  return res
})

mapState最终返回一个对象，然后可以通过扩展运算符来合并对象中的属性

js
const a = {a:1}
const b = {b:2}
console.log({...a, ...b}) // { a: 1, b: 2 }

const a = {a:1}
const b = {b:2}
console.log({...a, ...b}) // { a: 1, b: 2 }

normalizeMap

这个函数用于将对象和数组，转换成统一的数组格式 [{ key: 1, val: 1 }, { key: 2, val: 2 }, { key: 3, val: 3 }]，因为mapState这些函数可以传对象也可以传数组

js
/**
 * Normalize the map
 * normalizeMap([1, 2, 3]) => [ { key: 1, val: 1 }, { key: 2, val: 2 }, { key: 3, val: 3 } ]
 * normalizeMap({a: 1, b: 2, c: 3}) => [ { key: 'a', val: 1 }, { key: 'b', val: 2 }, { key: 'c', val: 3 } ]
 * @param {Array|Object} map
 * @return {Object}
 */
function normalizeMap(map) {
  if (!isValidMap(map)) {
    return []
  }
  return Array.isArray(map) ? map.map(key => ({ key, val: key })) : Object.keys(map).map(key => ({ key, val: map[key] }))
}

/**
 * Validate whether given map is valid or not
 * @param {*} map
 * @return {Boolean}
 */
function isValidMap(map) {
  // 判断是数组或是对象
  return Array.isArray(map) || isObject(map)
}

/**
 * Normalize the map
 * normalizeMap([1, 2, 3]) => [ { key: 1, val: 1 }, { key: 2, val: 2 }, { key: 3, val: 3 } ]
 * normalizeMap({a: 1, b: 2, c: 3}) => [ { key: 'a', val: 1 }, { key: 'b', val: 2 }, { key: 'c', val: 3 } ]
 * @param {Array|Object} map
 * @return {Object}
 */
function normalizeMap(map) {
  if (!isValidMap(map)) {
    return []
  }
  return Array.isArray(map) ? map.map(key => ({ key, val: key })) : Object.keys(map).map(key => ({ key, val: map[key] }))
}

/**
 * Validate whether given map is valid or not
 * @param {*} map
 * @return {Boolean}
 */
function isValidMap(map) {
  // 判断是数组或是对象
  return Array.isArray(map) || isObject(map)
}

createNamespacedHelpers

  • 创建基于某个命名空间辅助函数
  • 返回一个对象，对象中有新的绑定在（给定命名空间值上）的组件绑定辅助函数
js
import { createNamespacedHelpers } from 'vuex'
const { mapState, mapActions } = createNamespacedHelpers('main')
export default {
	computed: {
	//在`main`中查找
		...mapState({
			a: state => state.a
		})
	},
	methods: {
	//在`main`中查找
		...mapActions([
			'fn'
		])
	}
}

import { createNamespacedHelpers } from 'vuex'
const { mapState, mapActions } = createNamespacedHelpers('main')
export default {
	computed: {
	//在`main`中查找
		...mapState({
			a: state => state.a
		})
	},
	methods: {
	//在`main`中查找
		...mapActions([
			'fn'
		])
	}
}

源码

bind第一个参数null，表示不改变指向，第二个参数传入命名空间，返回相应命名空间对象

js
/**
 * Rebinding namespace param for mapXXX function in special scoped, and return them by simple object
 * @param {String} namespace
 * @return {Object}
 */
export const createNamespacedHelpers = namespace => ({
  mapState: mapState.bind(null, namespace),
  mapGetters: mapGetters.bind(null, namespace),
  mapMutations: mapMutations.bind(null, namespace),
  mapActions: mapActions.bind(null, namespace),
})

/**
 * Rebinding namespace param for mapXXX function in special scoped, and return them by simple object
 * @param {String} namespace
 * @return {Object}
 */
export const createNamespacedHelpers = namespace => ({
  mapState: mapState.bind(null, namespace),
  mapGetters: mapGetters.bind(null, namespace),
  mapMutations: mapMutations.bind(null, namespace),
  mapActions: mapActions.bind(null, namespace),
})

Released under the MIT License.

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