详解vuex中mapState,mapGetters,mapMutations,mapActions的作用

import Vuex from 'vuex' 
import Vue from 'vue' 
Vue.use(Vuex); 
const store = new Vuex.Store({ 
 state: { 
  count: 10, 
  numb: 10086 
 }, 
 getters: { 
  add: (state, getter) => { 
   state.count = getter.add; 
   return state.count; 
  }, 
 }, 
 mutations: { 
  increment(state,){ 
    state.count += 2; 
  }, 
 }, 
 actions: { 
  actionA({ dispatch, commit }) { 
   return commit('add'); 
  }, 
 } 
}); 

<template> 
 <div class="hello"> 
  <button @click="increment">加{{count}}</button> 
 </div> 
</template> 
<script> 
 import {mapState,mapActions} from 'vuex' 
 export default { 
  name: 'hello', 
  data () { 
   return { 
    msg: 'Welcome to Your Vue.js App' 
   } 
  }, 
  methods:{ 
   increment(){ 
    this.$store.dispatch('incrementsync').then(() => { 
     console.log('then'); 
    }); 
   } 
  }, 
  computed: mapState({ // mapState相当于映射 
    count: 'numb', //这个时候count应该等于多少？！！ 是等于store文件里面的count呢还是等于numb？答案是等于numb！这边的意思是mapState把'numb'的值映射给了count，所以count等于10086 
  }) 
 } 
</script>