在Vue中詳細解讀todoMVC程式碼

本篇文章主要介紹了Vue官網todoMVC範例程式碼，現在分享給大家，也給大家做個參考

這個範例是模仿官網範例樣式和功能用我自己的方式寫的，基本上沒有看官網的源碼，只參考自訂指令。讓我們一步步來探討一下。官網demo

要實現的功能

1. #單條新增todo

2. 單條刪除todo

3. 雙擊編輯todo

4. 單條todo已完成對應樣式狀態改變

5. 全部todo是已完成對應樣式狀態改變

6. 清除全部已完成todos

7. #待辦事項todos數量顯示

所有todos，已完成todos，未完成todos篩選

#單條添加todo

<input type="text" class="todos_add" placeholder="What needs to be done?" 
@keyup.enter="addTodo($event.target)" //绑定enter事件
ref="currentInput">//操作input元素使enter一下之后清空输入框内容

data() {//一些初始化数据
 return {
  todolists: [],
  dataStatus: ["All", "Active", "Completed"],
  dataStatusIndex: 0,
  whichShow: true,
  defaultShow: true
 }
},
addTodo(e) { //添加todo
 var val = e.value
 if (val === "") {return} //如果输入内容为空则立即返回
 this.todoLists = this.todoLists.concat({//使用concat这个api添加todo
  value: val, //输入内容
  isEditing: false, //是否在编辑状态
  isActive: false, //删除X图标是否激活
  isChecked: false //是否已完成
 })
 this.$refs.currentInput.value = "" //按下enter添加todo之后把输入框value清零
 window.localStorage.setItem("content",JSON.stringify(this.todoLists))//使用localStorage以JSON格式存储数据
},

#把每條todo的對應狀態都存在同一個物件當中，在操作改變todo狀態的時候不會被統一處理，使得每個todo都有單獨的狀態。

單條刪除todo

 <li class="content_todoList"
 v-for="(list,index) in todoLists" 
 @mouseover="list.isActive = true" //鼠标移入todo改变对应todo的isActive状态
 @mouseleave="list.isActive=false" //鼠标移出todo改变对应todo的isActive状态
 <span class="el-icon-close content_todoList_delete" 
 :class="{show: list.isActive}" //动态绑定class使鼠标移动到某一todo显示X图标
 @click="deleteTodo(index)"> //绑定删除单条todo事件
 </span>
</li>

deleteTodo(index) { //删除单条todo
  this.todoLists.splice(index, 1)//使用splice的api
  window.localStorage.setItem("content",JSON.stringify(todoLists)) //以JSON格式存储数据//localStorage存储数据
},

在每個li元素上綁定了滑鼠移入和移除的事件來動態的改變每個todo的isActive，然後再使用isActive動態顯示class。

雙擊編輯todo&&單條todo已完成

<input type="checkbox" class="checkBox" 
v-model="list.isChecked">//双向绑定isChecked

<p class="content_todoList_main" 
@dblclick="toEdit(list)" //双击事件
v-show="!list.isEditing" //切换元素
:class="{deleted:list.isChecked}"> //动态绑定class该表已完成todo样式
{{list.value}}
</p>

<input type="text" class="content_todoList_main main_input" 
v-model="list.value" //双向绑定可输入value
v-show="list.isEditing" //切换元素
v-todo-focus="list.value" //自定义指令，双击之后自动focus对焦
@blur="unEdit(list)"> //绑定blur失去焦点事件

methods: {
 toEdit(obj) { //使添加的todothing可编辑
  obj.isEditing = true
 },
 
 unEdit(obj) { //使添加的todothing不可编辑
  obj.isEditing = false
 },
}

directives: { //自定义focus指令,需要一个binding参数做判断
 "todo-focus": function (el, binding) {
  if (binding.value) {
   el.focus()
  }
 }
}

透過每個todo裡的isEditing屬性控制show和是否可編輯兩個狀態，雙擊p之後改變目前todo的isEditing為true，因而顯示為input，input失去焦點之後再透過blur事件改為false。

透過todo的idChecked來控制是否已完成，從而動態改變樣式。

全部todos已完成

<span 
class="icon-down el-icon-arrow-down" //使用element库做向下箭头icon
v-show="todoLists.length>0" //通过todoLists控制是否显示向下箭头icon
@click="selectAllTodos"></span> //全部已完成事件

selectAllTodos() { //设置所有todo为已完成,使用map的api通过todo的isChecked属性操作
 this.todoLists.map(todo => todo.isChecked = todo.isChecked ? false : true)
}

待辦todos數量顯示

<p class="data_times" v-show="times === 0"> //times为0显示item，大于0显示items，细节注定成败
 <span>{{times}}</span>&nbsp item left
</p>
<p class="data_times" v-show="times > 0">
<span>{{times}}</span>&nbsp items left</p>

computed: {
 times() { //使用计算属性计算待办todos的次数 
  let todoArr = this.todoLists
  let times = 0
  for (let i = 0; i < todoArr.length; i++) {
   if (todoArr[i].isChecked === false) {
    times++
   }
  }
  return times
 }
},

使用了計算屬性對todoLists計算，用for循環刷選出idChecked為true的累加，最後回傳times。

清除全部已完成todos

<p class="data_clearTodos" 
@click="clearTodos" 
v-show="times < todoLists.length"> //如果待办事件次数小于总todoLists长度就显示“clear completed”
 <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >clear completed</a>
</p>

<p class="data_clearTodos" 
@click="clearTodos" 
v-show="times === todoLists.length"> //如果待办事件次数等于总todoLists长度就显示“clear completed”
 <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></a>
</p>

clearTodos() { //清空已完成的todoLists，使用filter的api进行筛选
 this.todoLists = this.todoLists.filter(todo => todo.isChecked === false)
 window.localStorage.setItem("content",JSON.stringify(this.todoLists)) //以json格式存储数据
},

如果待辦todos的times小於todoLists長度，就證明有已完成的todo，就可以顯示“clear completed”，如果相等就表示沒有已完成的todo。

三種狀態篩選

所有todos，已完成todos，未完成todos篩選

<li class="content_todoList" 
v-show="defaultShow || (whichShow?list.isChecked:!list.isChecked)">

<p class="data_status">
 <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" 
 :class="{active: index === dataStatusIndex}" //动态class实现tab切换
 v-for="(item ,index) in dataStatus" v-for循环
 @click="switchStatus(index)" //切换不同tab显示内容
 :key="index">
  {{item}}
 </a>
</p>

switchStatus(index) { //通过if条件判断操作
 this.dataStatusIndex = index
 if (this.dataStatus[index] === "Active") {
  this.defaultShow = false
  this.whichShow = false
 } else if (this.dataStatus[index] === "Completed") {
  this.defaultShow = false
  this.whichShow = true
 } else if (this.dataStatus[index] === "All") {
  this.defaultShow = true
 }
},

我這裡是同時if條件句判斷操作，有點麻煩，目前還沒想出來其他方案。在li元素使用三元運算子和或運算子進行操作顯示不同狀態的todos。

完整程式碼

<style>
 * {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
 }

 input {
  outline: none;
 }

 ul,
 li,
 ol {
  list-style: none;
 }

 #app {
  width: 800px;
  height: 900px;
  margin: 0 auto;
  text-align: center;
  background-color: rgb(245, 245, 245);
  padding: 24px 0;
 }

 #app .header {
  font-size: 48px;
 }

 .content {
  width: 72%;
  margin: 0 auto;
  box-shadow: 0 3px 3px 2px rgba(0, 0, 0, 0.25);
  position: relative;
 }

 .icon-down {
  position: absolute;
  font-size: 24px;
  top: 16px;
  left: 16px;
  cursor: pointer;
 }

 #app .content .todos_add {
  width: 100%;
  height: 56px;
  padding: 16px 56px;
  font-size: 24px;
  border: 1px solid transparent;
 }

 .content_todoLists {
  position: relative;
  z-index: 3;
 }

 .content_todoList {
  display: flex;
  flex-direction: row;
  border-top: 1px solid #ccc;
  font-size: 24px;
  padding: 8px;
  background-color: white;
  align-items: center;
 }

 .checkBox {
  width: 20px;
  height: 20px;
  margin-left: 10px;
 }

 .content_todoList_main {
  flex: 1;
  text-align: left;
  margin-left: 16px;
  font-size: 20px;
  padding: 6px 0;
 }

 .main_input {
  position: relative;
  z-index: 1;
 }

 .content_todoList_delete {
  position: absolute;
  right: 16px;
  color: rgb(252, 55, 55);
  font-weight: 500;
  display: none;
  cursor: pointer;
 }

 .show {
  display: block;
 }

 .deleted {
  text-decoration-line: line-through;
  color: #bbb;
 }

 .show:hover {
  color: rgb(255, 0, 0);
  font-weight: 700;
 }

 ::-moz-placeholder {
  color: rgb(221, 218, 218);
 }

 ::-webkit-input-placeholder {
  color: rgb(221, 218, 218);
 }

 :-ms-input-placeholder {
  color: rgb(221, 218, 218);
 }

 .data {
  display: flex;
  justify-content: space-between;
  padding: 8px;
  font-size: 14px;
  font-weight: 300;
  color: rgb(145, 145, 145);
 }

 a {
  text-decoration: none;
  color: rgb(145, 145, 145);
 }

 .data_times {
  width: 73px;
 }

 .data_clearTodos {
  width: 142px;
 }

 .data_status a {
  display: inline-block;
  border: 1px solid transparent;
  border-radius: 2px;
  padding: 1px 4px;
  margin: 0 2px;
 }

 .data_status a:hover {
  border-color: #bbb;
 }

 .data_clearTodos a:hover {
  text-decoration-line: underline;
 }

 .active {
  box-shadow: 0 0 1px black;
 }
</style>

<body>
 <p id="app">
  <header class="header">todos</header>
  <p class="content">
   <span class="icon-down el-icon-arrow-down" 
   v-show="todoLists.length>0" 
   @click="selectAllTodos">
   </span>
   <input type="text" class="todos_add" placeholder="What needs to be done?" 
   @keyup.enter="addTodo($event.target)" 
   ref="currentInput">
   <ul class="content_todoLists">
    <li v-for="(list,index) in todoLists" class="content_todoList" 
    @mouseover="list.isActive = true" 
    @mouseleave="list.isActive=false"
    v-show="defaultShow || (whichShow?list.isChecked:!list.isChecked)">
     <input type="checkbox" class="checkBox" v-model="list.isChecked">
     <p class="content_todoList_main" @dblclick="toEdit(list)" v-show="!list.isEditing" :class="{deleted:list.isChecked}">
      {{list.value}}
     </p>
     <input type="text" class="content_todoList_main main_input" 
     v-model="list.value" 
     v-show="list.isEditing" 
     v-todo-focus="list.value"
     @blur="unEdit(list)">
     <span class="el-icon-close content_todoList_delete" :class="{show: list.isActive}" @click="deleteTodo(index)"></span>
    </li>
   </ul>
   <p class="data" v-show="todoLists.length>0">
    <p class="data_times" v-show="times === 0">
     <span>{{times}}</span>&nbspitem left
    </p>
    <p class="data_times" v-show="times > 0">
     <span>{{times}}</span>&nbspitems left
    </p>
    <p class="data_status">
     <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" :class="{active:index === dataStatusIndex}" v-for="(item,index) in dataStatus" @click="switchStatus(index)" :key="index">
      {{item}}
     </a>
    </p>
    <p class="data_clearTodos" @click="clearTodos" v-show="times < todoLists.length">
     <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >clear completed</a>
    </p>
    <p class="data_clearTodos" @click="clearTodos" v-show="times === todoLists.length">
     <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></a>
    </p>
   </p>
  </p>
 </p>
</body>
<script>
 let vm = new Vue({
  el: "#app",
  data() {
   return {
    todoLists: [],
    dataStatus: ["All", "Active", "Completed"],
    dataStatusIndex: 0,
    whichShow: true,
    defaultShow: true
   }
  },
  computed: {
   times() { //使用计算属性计算待办todos的次数 
    let todoArr = this.todoLists
    let times = 0
    for (let i = 0; i < todoArr.length; i++) {
     if (todoArr[i].isChecked === false) {
      times++
     }
    }
    return times
   }
  },
  methods: {
   toEdit(obj) { //使添加的todo可编辑
    obj.isEditing = true
   },
   unEdit(obj) { //使添加的todo不可编辑
    obj.isEditing = false
   },
   addTodo(e) { //添加todo
    var val = e.value
    if (val === "") {
     return
    } //如果输入内容为空则立即返回
    this.todoLists = this.todoLists.concat({ //使用concat这个api添加todo
     value: val, //输入内容
     isEditing: false, //是否在编辑状态
     isActive: false, //删除X图标是否激活
     isChecked: false //是否已完成
    })
    this.$refs.currentInput.value = "" //按下enter添加todo之后把输入框value清零
    window.localStorage.setItem("content", JSON.stringify(this.todoLists)) //使用localStorage以JSON格式存储数据
   },
   deleteTodo(index) { //删除todo
    this.todoLists.splice(index, 1)
    window.localStorage.setItem("content", JSON.stringify(this.todoLists)) //以json格式存储数据
   },
   switchStatus(index) { //试下下方三个状态切换，略麻烦
    this.dataStatusIndex = index
    if (this.dataStatus[index] === "Active") {
     this.defaultShow = false
     this.whichShow = false
    } else if (this.dataStatus[index] === "Completed") {
     this.defaultShow = false
     this.whichShow = true
    } else if (this.dataStatus[index] === "All") {
     this.defaultShow = true
    }
   },
   clearTodos() { //清空已完成的todoLists
    this.todoLists = this.todoLists.filter(todo => todo.isChecked === false)
    window.localStorage.setItem("content", JSON.stringify(this.todoLists)) //以json格式存储数据
   },
   selectAllTodos() { //设置所有todo为已完成
    this.todoLists.map(todo => todo.isChecked = todo.isChecked ? false : true)
   }
  },
  directives: { //自定义focus指令
   "todo-focus": function (el, binding) {
    if (binding.value) {
     el.focus()
    }
   }
  },
  created() {
   let myStorage = window.localStorage.getItem(&#39;content&#39;)
   this.todoLists = JSON.parse(myStorage) || [] //因为todoLists初始值是null,使用或运算符，如果为null设为空数组
  }
 })
</script>

上面是我整理給大家的，希望今後會對大家有幫助。

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