vueX

let Vue;
const install = (_Vue) => {
  // 先判断是否use过
  if (Vue && _Vue === Vue) {
    console.error('[vuex] already installed. Vue.use(Vuex) should be called only once.')
    return
  }
  // 绑定Vue的构造函数
  Vue = _Vue
  // 判断Vue版本，2版本推荐用mixin
  // 1版本单例，放到原型上（会影响其他Vue实例）
  const version = Number(Vue.version.split('.')[0])
  if (version >= 2) {
    Vue.mixin({
      beforeCreate() {
        const options = this.$options
        // store injection
        if (options.store) {
          this.$store = typeof options.store === 'function'
            ? options.store()
            : options.store
        } else if (options.parent && options.parent.$store) {
          this.$store = options.parent.$store
        }
      }
    })
  } else {
    // override init and inject vuex init procedure
    // for 1.x backwards compatibility.
    const _init = Vue.prototype._init
    Vue.prototype._init = function (options = {}) {
      options.init = options.init
        ? [vuexInit].concat(options.init)
        : vuexInit
      _init.call(this, options)
    }
  }
}
class Store {
    construtor(options = {}) {
    this._vm = new Vue({
      data: {
        stage: options.state,
      }
    })
    let getters = options.getters;
    this.getters = {}
    Object.keys(getters).forEach(getterName => {
      Object.defineProperty(this.getters, getterName, {
        get: () => getters[getterName](this.state)
        enumerable: true, // for local getters
      })
    })
  }
  get state () {
    return this._vm._data.$$state
  }
  set state (v) {
    if (__DEV__) {
      assert(false, `use store.replaceState() to explicit replace store state.`)
    }
  }
  commit = (type, payload, options) => {
  }
}
 export default {
  Store,
  install,
}