mutations狀態更改

　　在mutations對象中創建更改state狀態的方法。mapMutations是vuex提供的輔助函數

在store.js中

import Vue from ‘vue‘
import Vuex from ‘vuex‘

Vue.use(Vuex)

//訪問狀態對象
const state = {
    count:1
}

// 觸發的狀態，mutations是同步的
const mutations = {
    jian(state){//傳入一個state對象
        state.count--
    },
    jia(state,n){
        state.count
 
+=n.a
    }
}


export default new Vuex.Store({
    state,
    mutations
})

在App.vue文件中

<template>
  <div id="app">
    
    <img src="./assets/logo.png">
    <h1>{{ msg}}</h1>
    <!--訪問狀態對象-->
    <div>使用mutation觸發改變狀態-->{{$store.state.count}}</div>
    <!--用commit訪問觸發的mutations裏面的方法-->
    <button @click="
 
$store.commit(‘jia‘,{a:10})">+</button>
    <!--使用mapMutations-->
    <button @click="jian">-</button>
  </div>
</template>

<script>

//vuex提供的輔助函數
import {mapState,mapMutations,mapGetters,mapActions} from ‘vuex‘
export default {
  name: ‘app‘,
  data () {
    return {
      msg: 
 
‘Welcome to Your Vue.js App‘
    }
  },
  
  //解決頁面白屏問題
  mounted(){
    if(app.hasChildNodes()){
          loading.style.display="none";
       }else{
         console.log(app.childNodes)
       }
  },

  // methods:mapMutations([
  //   ‘jian‘
  // ])
  methods:{
    ...mapMutations([//
      ‘jian‘
    ])
  }
}
</script>

<style>
#app {
  font-family: ‘Avenir‘, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}

h1, h2 {
  font-weight: normal;
}

ul {
  list-style-type: none;
  padding: 0;
}

li {
  display: inline-block;
  margin: 0 10px;
}

a {
  color: #42b983;
}
</style>

3.vuex學習之mutations、mapMutations