$ npm install -g vue-cli
$ vue init ，比如 vue init webpack todolist
$ cd todolist
$ npm install
$ npm run dev

//后面的为注释讲解， ~表示串联index.html的对应内容

import 'todomvc-app-css/index.css'
import Vue from 'vue'
//添加localStorage
var STORAGE_KEY = 'todos-vuejs-2.0'
var todoStorage = {
 fetch: function () {
  var todos = JSON.parse(localStorage.getItem(STORAGE_KEY) || '[]')
  todos.forEach(function (todo, index) {
   todo.id = index
  })
  todoStorage.uid = todos.length
  return todos
 },
 save: function (todos) {
  localStorage.setItem(STORAGE_KEY, JSON.stringify(todos))
 }
}
//用过滤器筛选出三种状态
var filters = {
 all(todos) {
  return todos
 },
 active(todos) {
  return todos.filter((todo) => {
   return !todo.completed
  })
 },
 completed(todos) {
  return todos.filter((todo) => {
   return todo.completed
  })
 },
}
let app = new Vue({
 el: '.todoapp',  // ~ <section class="todoapp">
 data: {
  msg: 'hello world',
  title: '待做清单',  // 渲染标题 ~ {{title}}
  newTodo: '',
   todos: todoStorage.fetch(), // ~ v-show="todos.length" ； ~ {{todos.length>1"(todo,index) in filteredTodos" 
  editedTodo: '',  // 空的编辑对象
  hashName: 'all'  
 },
 
 watch: {
  todos: {
   handler: function (todos) {
    todoStorage.save(todos)
   },
   deep: true
  }
 },
 
 computed: {
  remain() {
   return filters.active(this.todos).length  //未完成事项的数量 ~ {{remain}}
  }, 
  isAll: {   // ~ v-model="isAll"
   get() {
    return this.remain === 0
   },
   set(value) {
    this.todos.forEach((todo) => {
     todo.completed = value
    })
   }
  },
  filteredTodos() {  //用hashName过滤出当前页面的todos ~ v-for="(todo,index) in filteredTodos" 
   return filters[this.hashName](this.todos)
  }
 },
 methods: {
  addTodo(e) { //输入值为空时，不添加（trim去除前后空格） ~ v-model.trim="newTodo" 
   if (!this.newTodo) {
    return
   }
   this.todos.push({
    id: todoStorage.uid++,
    content: this.newTodo,
    completed: false //结合v-model 根据completed状态绑定样式 ~:class="{completed:todo.completed； ~ v-model="todo.completed"
   })
   this.newTodo = ''
  },
  removeTodo(index) {  //绑定x样式，点击删除该todo ~ @click="removeTodo(index)"
   this.todos.splice(index, 1)
  },
  editTodo(todo) {     //编辑 ~ @dblclick="editTodo(todo)"
   this.editCache = todo.content //储存编辑前的内容
   this.editedTodo = todo // 点击编辑里面的内容而不是只是空文本框~ editing:todo==editedTodo}"
  },
  doneEdit(todo, index) { //失去焦点后 ~ @blur="doneEdit(todo)"；@keyup.enter="doneEdit(todo)"
   this.editedTodo = null //不存在编辑了或者说编辑已完成
   if (!todo.content) { //如果编辑后没有内容了，删除该todo
    this.removeTodo(index)
   }
  },
  cancelEdit(todo) {  //按esc键取消此次编辑操作 ~ @keyup.esc="cancelEdit(todo)">
   this.editedTodo = null   
   todo.content = this.editCache //当esc取消编辑时，还原编辑前的内容
  },
  clear() { //点击清除已完成的功能 ~ @click="clear"
   this.todos = filters.active(this.todos) //获取并渲染未完成的事项 ~ 
  }
 },
 directives: {  //自定义属性 ~ v-focus="todo == editedTodo"
  focus(el, value) { //文本框双击获取焦点
   if (value) {
    el.focus()
   }
  }
 }
})
//hash（url地址中#以及之后的字符）
function hashChange() { 
// ~ :class="{selected:hashName=='all'}"；:class="{selected:hashName=='active'}"；:class="{selected:hashName=='completed'}"
 let hashName = location.hash.replace(/#\/?/, '') //正则表达式去除#/？，获取如all，active，completed
 if (filters[hashName]) {  //如果过滤状态的hashName存在
  app.hashName = hashName //给整个app变量里的hashName赋上那个值
 } else {
  location.hash = ''  //取消
  app.hashName = 'all' //否则就赋值‘all'，回到全部事项的页面
 }
}
window.addEventListener('hashchange', hashChange) //全局监听hash