//state.js
const state = {
 headerBgOpacity:0,
 loginStatus:0,
 count:66
}
export default state
//index.js
import Vue from 'vue'
import Vuex from 'vuex'
import state from './state'
import actions from './actions'
import getters from './getters'
import mutations from './mutations'
Vue.use(Vuex)
export default new Vuex.Store({
 state,
 actions,
 getters,
 mutations
})

<template>
 <div class="test">
  {{$store.state.count}} <!--第一种方式-->
 </div>
</template>
<script type="text/ecmascript-6">
 export default{
  name:'test',
  data(){
   return{ }
  }
 }
</script>
<style>
</style>

<template>
 <div class="test">
  {{count}} <!--步骤二-->
 </div>
</template>
<script type="text/ecmascript-6">
 export default{
  name:'test',
  data(){
   return{}
  },
  computed:{
   count(){
    return this.$store.state.count; //步骤一
   }
  }
 }
</script>
<style>
</style>

<template>
 <div class="test">
  {{count}} <!--步骤三-->
 </div>
</template>
<script type="text/ecmascript-6">
 import {mapState} from 'vuex' //步骤一
 export default{
  name:'test',
  data(){
   return{}
  },
  computed:mapState({     //步骤二,对象方式
   count:state => state.count
  })
 }
</script>
<style>
</style>

<template>
 <div class="test">
  {{count}} <!--步骤三-->
 </div>
</template>
<script type="text/ecmascript-6">
 import {mapState} from 'vuex' //步骤一
 export default{
  name:'test',
  data(){
   return{}
  },
  computed:mapState([    //步骤二,数组方式
   "count"
  ])
 }
</script>
<style>
</style>

<template>
 <div class="test">
  {{count}} <!--步骤三-->
 </div>
</template>
<script type="text/ecmascript-6">
 import {mapState} from 'vuex' //步骤一
 export default{
  name:'test',
  data(){
   return{}
  },
  computed:{
   ...mapState([       //步骤二，三个点方式
    "count"
   ])
  }
 }
</script>
<style>
</style>