这个示例是模拟官网示例款式和功用用我本身的体式格局写的，基本上没有看官网的源码，只参考自定义指令。让我们一步步来讨论一下。官网demo

要完成的功用

1. 单条增加todo
2. 单条删除todo
3. 双击编辑todo
4. 单条todo已完成响应款式状况转变
5. 悉数todo是已完成响应款式状况转变
6. 消灭悉数已完成todos
7. 待办todos数目显现
8. 一切todos，已完成todos，未完成todos挑选

单条增加todo

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

data() {//一些初始化数据
    return {
        todolists: [],
        dataStatus: ["All", "Active", "Completed"],
        dataStatusIndex: 0,
        whichShow: true,
        defaultShow: true
    }
},

addTodo(e) { //增加todo
    var val = e.value
    if (val === "") {return} //假如输入内容为空则马上返回
    this.todoLists = this.todoLists.concat({//运用concat这个api增加todo
        value: val, //输入内容
        isEditing: false, //是不是在编辑状况
        isActive: false, //删除X图标是不是激活
        isChecked: false //是不是已完成
    })
    this.$refs.currentInput.value = "" //按下enter增加todo以后把输入框value清零
    window.localStorage.setItem("content",JSON.stringify(this.todoLists))//运用localStorage以JSON花样存储数据
},

把每条todo的对应状况都存在同一个对象当中，在操纵转变todo状况的时刻不会被一致处置惩罚，使得每条todo都有零丁的状况。

单条删除todo

 <li  class="content_todoList"
 v-for="(list,index) in todoLists" 
 @mouseover="list.isActive = true" //鼠标移入todo转变对应todo的isActive状况
 @mouseleave="list.isActive=false" //鼠标移出todo转变对应todo的isActive状况
    <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显现X图标
    @click="deleteTodo(index)"> //绑定删除单条todo事宜
    </span>
</li>

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

在每一个li元素上绑定了鼠标移入和移除的事宜来动态的转变每一个todo的isActive，然后再运用isActive动态显现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)" //双击事宜
v-show="!list.isEditing" //切换元素
:class="{deleted:list.isChecked}"> //动态绑定class该表已完成todo款式
{{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，双击以后自动focus对焦
@blur="unEdit(list)"> //绑定blur落空核心事宜

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

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

经由过程每一个todo里的isEditing属性掌握show和是不是可编辑两个状况，双击div以后转变当前todo的isEditing为true，从而显现为input，input落空核心以后再经由过程blur事宜改成false。
经由过程todo的idChecked来掌握是不是已完成，从而动态转变款式。

悉数todos已完成

<span 
class="icon-down el-icon-arrow-down" //运用element库做向下箭头icon
v-show="todoLists.length>0" //经由过程todoLists掌握是不是显现向下箭头icon
@click="selectAllTodos"></span> //悉数已完成事宜

selectAllTodos() { //设置一切todo为已完成,运用map的api经由过程todo的isChecked属性操纵
    this.todoLists.map(todo => todo.isChecked = todo.isChecked ? false : true)
}

待办todos数目显现

<div class="data_times" v-show="times === 0"> //times为0显现item，大于0显现items，细节必定成败
    <span>{{times}}</span>&nbsp item left
</div>
<div class="data_times" v-show="times > 0">
<span>{{times}}</span>&nbsp items left</div>

computed: {
    times() { //运用盘算属性盘算待办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
    }
},

运用了盘算属性对todoLists盘算，用for轮回刷选出idChecked为true的累加，末了返回times。

消灭悉数已完成todos

<div class="data_clearTodos" 
@click="clearTodos" 
v-show="times < todoLists.length"> //假如待办事宜次数小于总todoLists长度就显现“clear completed”
    <a href="#">clear completed</a>
</div>

<div class="data_clearTodos" 
@click="clearTodos" 
v-show="times === todoLists.length"> //假如待办事宜次数即是总todoLists长度就显现“clear completed”
    <a href="#"></a>
</div>

clearTodos() { //清空已完成的todoLists，运用filter的api举行挑选
    this.todoLists = this.todoLists.filter(todo => todo.isChecked === false)
    window.localStorage.setItem("content",JSON.stringify(this.todoLists)) //以json花样存储数据
},

假如待办todos的times小于todoLists长度，就证实有已完成的todo，就能够显现“clear completed”，假如相称就申明没有已完成的todo。

三种状况挑选

一切todos，已完成todos，未完成todos挑选

<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完成tab切换
    v-for="(item ,index) in dataStatus" v-for轮回
    @click="switchStatus(index)" //切换差别tab显现内容
    :key="index">
        {{item}}
    </a>
</div>

switchStatus(index) { //经由过程if前提推断操纵
    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
    }
},

我这里是同时if前提句推断操纵，有点贫苦，现在还没有想出来其他计划。在li元素运用三元运算符和或运算符举行操纵显现差别状况的todos。

完全代码

<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>
    <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() { //运用盘算属性盘算待办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) { //使增加的todo可编辑
                obj.isEditing = true
            },
            unEdit(obj) { //使增加的todo不可编辑
                obj.isEditing = false
            },
            addTodo(e) { //增加todo
                var val = e.value
                if (val === "") {
                    return
                } //假如输入内容为空则马上返回
                this.todoLists = this.todoLists.concat({ //运用concat这个api增加todo
                    value: val, //输入内容
                    isEditing: false, //是不是在编辑状况
                    isActive: false, //删除X图标是不是激活
                    isChecked: false //是不是已完成
                })
                this.$refs.currentInput.value = "" //按下enter增加todo以后把输入框value清零
                window.localStorage.setItem("content", JSON.stringify(this.todoLists)) //运用localStorage以JSON花样存储数据
            },
            deleteTodo(index) { //删除todo
                this.todoLists.splice(index, 1)
                window.localStorage.setItem("content", JSON.stringify(this.todoLists)) //以json花样存储数据
            },
            switchStatus(index) { //试下下方三个状况切换，略贫苦
                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花样存储数据
            },
            selectAllTodos() { //设置一切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) || [] //由于todoLists初始值是null,运用或运算符，假如为null设为空数组
        }
    })
</script>