new Vuex.Store({})

state：{}

store.state.数据

mutations: {}

<div id="app"></div>

<template id="tpl">
  <div>
    <tip></tip>
    <but></but>
  </div>
</template>

<script>

  var store = new Vuex.Store({
    state:{
      count:0
    },
    mutations:{
      jia (state) {
        state.count++
      },
      jian (state) {
        state.count--
      }
    }
  });

  var vm = new Vue({
    el:"#app",
    template:"#tpl",
    components:{
      tip:{
        template:"<div>{{$store.state.count}}</div>"
      },
      but:{
        template:`
          <div>
            <input type="button" value="+" @click="$store.commit('jia')"/>
            <input type="button" value="-" @click="$store.commit('jian')"/>  
          </div>
        `
      }
    },
    store
  });
</script>

<script>
  //我们从store里面获取的数据最好放到计算属性中
  var store = new Vuex.Store({
    state:{
      count:0,
      num1:1,
      num2:2
    },
    mutations:{
      jia (state) {
        state.count++
      },
      jian (state) {
        state.count--
      }
    }
  });
  var vm = new Vue({
    el:"#app",
    template:"#tpl",
    components:{
      tip:{
      //创建计算属性
      
        // computed:{
        //   count(){
        //     return this.$store.state.count;
        //   },
        //   num1(){
        //     return this.$store.state.num1;
        //   },
        //   num2(){
        //     return this.$store.state.num2;
        //   }
        // },
        //使用mapState辅助函数
        //computed:Vuex.mapState({
          // count:state=>state.count,
          //num1:state=>state.num1,
          //num2:state=>state.num2
        //}),
        //mapState 传一个字符串数组
        computed:Vuex.mapState(['count' , 'num1' , 'num2']),
        template:"<div>{{count}}{{num1}}{{num2}}</div>"
      },
      but:{
        template:`
          <div>
            <input type="button" value="+" @click="$store.commit('jia')"/>
            <input type="button" value="-" @click="$store.commit('jian')"/>  
          </div>
        `
      }
    },
    store
  });
</script>