const moduleA = {state: { ... },mutations: { ... },actions: { ... },getters: { ... }
}const moduleB = {state: { ... },mutations: { ... },actions: { ... }
}const store = new Vuex.Store({modules: {a: moduleA,b: moduleB}
})store.state.a // -> moduleA 的状态
store.state.b // -> moduleB 的状态

import Vuex from 'vuex';
Vue.use(Vuex); // 1. vue的插件机制，安装vuex
let store = new Vuex.Store({ // 2.实例化store，调用install方法state,getters,modules,mutations,actions,plugins
});
new Vue({ // 3.注入store, 挂载vue实例store,render: h=>h(app)
}).$mount('#app');

import Vuex from 'vuex';
Vue.use(vuex);// vue的插件机制

export function install (_Vue) {if (Vue && _Vue === Vue) {if (process.env.NODE_ENV !== 'production') {console.error('[vuex] already installed. Vue.use(Vuex) should be called only once.')}return}Vue = _VueapplyMixin(Vue)
}

Vue.mixin({ beforeCreate: vuexInit });function vuexInit () {const options = this.$options// store injectionif (options.store) {this.$store = typeof options.store === 'function'? options.store(): options.store} else if (options.parent && options.parent.$store) {this.$store = options.parent.$store}
}

function resetStoreVM (store, state, hot) {const oldVm = store._vm// 设置 getters 属性store.getters = {}const wrappedGetters = store._wrappedGettersconst computed = {}// 遍历 wrappedGetters 属性forEachValue(wrappedGetters, (fn, key) => {// 给 computed 对象添加属性computed[key] = partial(fn, store)// 重写 get 方法// store.getters.xx 其实是访问了store._vm[xx]，其中添加 computed 属性Object.defineProperty(store.getters, key, {get: () => store._vm[key],enumerable: true // for local getters})})const silent = Vue.config.silentVue.config.silent = true// 创建Vue实例来保存state，同时让state变成响应式// store._vm._data.$$state = store.statestore._vm = new Vue({data: {$$state: state},computed})Vue.config.silent = silent// 只能通过commit方式更改状态if (store.strict) {enableStrictMode(store)}
}