const STORAGE_KEY = 'todos-vue.js'
export default{
  fetch(){
    return JSON.parse(window.localStorage.getItem(STORAGE_KEY) || '[]')
  },
  save(items){
    window.localStorage.setItem(STORAGE_KEY,JSON.stringify(items));
  }
}

<template>
 <div id="app">
  <h1 v-text="title"></h1>
  <input v-model="newItem" v-on:keyup.enter="addNew"/>
  <ul>
   <li v-for="item in items" v-bind:class="{finished:item.isFinished}" v-on:click='toogleFinish(item)'>
    {{item.label}}
   </li>
  </ul>
  <!-- 使用組件，注意駝峰命名法轉化成短線 -->
  <!-- 向自組件傳數據 -->
  <Component-a msgfromfather='you die!'></Component-a>
 </div>
</template>
<script>
import Store from './store'
import ComponentA from './components/componentA'  //該組件會被加載到該頁面
export default {
 name: 'app',
 data () {
  return {
   title: 'this is a todo list',
   items:Store.fetch(),
   newItem:''
  }
 },
 components:{ //注冊組件
  ComponentA
 },
 watch:{
   items:{
    handler(items){   //經過變化的數組會作為第一個參數傳入
     Store.save(items)
    },
    deep:true    //深度復制
   }
 },
 methods:{
  toogleFinish(item){
   item.isFinished = !item.isFinished
  },
  addNew(){
   this.items.push({
    label:this.newItem,
    isFinished:false,
   })
   this.newItem = ''
  }
 }
}
</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;
}
.finished{
 text-decoration: underline;
}
</style>

<template>
 <div class="hello">
  <h1>{{msg}}</h1>
  <h2>{{msgfromfather}}</h2>
  <button v-on:click="onClickMe">Click!</button>
 </div>
</template>
<<script>
export default {
 data(){
   return{
     msg:'Hello form component a'
   }
 },
 props:['msgfromfather'],//自組件接收數據
 methods:{
   onClickMe(){
     console.log(this.msgfromfather);
   }
 }
}
</script>
<style scoped>
</style>