这个示例是模仿官网示例样式和功能用我自己的方式写的，基本上没有看官网的源码，只参考自定义指令。让我们一步步来探讨一下。官网demo

要实现的功能

1. 单条添加todo
2. 单条删除todo
3. 双击编辑todo
4. 单条todo已完成相应样式状态改变
5. 全部todo是已完成相应样式状态改变
6. 清除全部已完成todos
7. 待办todos数量显示
8. 所有todos，已完成todos，未完成todos筛选

单条添加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todovar val = e.valueif (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todovalue: 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
},

把每条todo的对应状态都存在同一个对象当中，在操作改变todo状态的时候不会被统一处理，使得每条todo都有单独的状态。

单条删除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todothis.todoLists.splice(index, 1)//使用splice的apiwindow.localStorage.setItem("content",JSON.stringify(todoLists)) //以JSON格式存储数据//localStorage存储数据
},

在每个li元素上绑定了鼠标移入和移除的事件来动态的改变每个todo的isActive，然后再使用isActive动态显示class。

双击编辑todo&&单条todo已完成

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

<div 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}}
</div>

<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()
}
}
}
```

通过每个todo里的isEditing属性控制show和是否可编辑两个状态，双击div之后改变当前todo的isEditing为true，从而显示为input，input失去焦点之后再通过blur事件改为false。
通过todo的idChecked来控制是否已完成，从而动态改变样式。

全部todos已完成

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)
}

待办todos数量显示

<div 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 </div> <div class="data_times" v-show="times > 0"> <span>{{times}}</span>&nbsp items left</div>

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

使用了计算属性对todoLists计算，用for循环刷选出idChecked为true的累加，最后返回times。

清除全部已完成todos

```<div 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="#">clear completed</a>
</div>

<div 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="#"></a>
</div>

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
},
```

如果待办todos的times小于todoLists长度，就证明有已完成的todo，就可以显示“clear completed”，如果相等就说明没有已完成的todo。

三种状态筛选

所有todos，已完成todos，未完成todos筛选

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

<div class="data_status">
<a href="#"
: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>
</div>

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
}
},

<p>我这里是同时if条件句判断操作，有点麻烦，目前还没有想出来其他方案。在<code>li</code>元素使用三元运算符和或运算符进行操作显示不同状态的todos。</p>
<h1>完整代码</h1>

<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>
```

    <div id="app"><header class="header">todos</header><div 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"><div class="content_todoList_main" @dblclick="toEdit(list)" v-show="!list.isEditing" :class="{deleted:list.isChecked}">{{list.value}}</div><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><div class="data" v-show="todoLists.length>0"><div class="data_times" v-show="times === 0"><span>{{times}}</span>&nbspitem left</div><div class="data_times" v-show="times > 0"><span>{{times}}</span>&nbspitems left</div><div class="data_status"><a href="#" :class="{active:index === dataStatusIndex}" v-for="(item,index) in dataStatus" @click="switchStatus(index)" :key="index">{{item}}</a></div><div class="data_clearTodos" @click="clearTodos" v-show="times < todoLists.length"><a href="#">clear completed</a></div><div class="data_clearTodos" @click="clearTodos" v-show="times === todoLists.length"><a href="#"></a></div></div></div></div>
</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.todoListslet times = 0for (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todovar val = e.valueif (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todovalue: 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todothis.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 = indexif (this.dataStatus[index] === "Active") {this.defaultShow = falsethis.whichShow = false} else if (this.dataStatus[index] === "Completed") {this.defaultShow = falsethis.whichShow = true} else if (this.dataStatus[index] === "All") {this.defaultShow = true}},clearTodos() { //清空已完成的todoListsthis.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('content')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>

原文地址：https://segmentfault.com/a/1190000013026721