[vuex] must call Vue.use(Vuex) b

调用vuex的时候报了这个错误

就是在调用vuex之前，要是用vue.use(Vuex)来调用vuex

import Vuex from 'vuex'
import Vue from 'vue'

 Vue.use(Vuex)

const store = new Vuex.Store({
  state: {
    count: 0
  },
  mutations: {
    updateCount (state, num) {
      state.count = num
    }
  }
})
export default store