初级使用e.target.value 

记得安装npm i nanoid与UUID类似 快捷键ctrl+H替换内容

src/components/MyHeader.vue

<template>
    <div class="todo-header">
        <input type="text" placeholder="请输入你的任务名称，按回车键确认" v-model="title" @keyup.enter="add()" />
    </div>
</template>

<script>
import {nanoid} from 'nanoid'
export default {
    name: 'MyHeader',
    data(){
        return{
            title:''
        }
    },
    props:['addToDo'],
    methods:{
        add(){
            if(!this.title.trim()) return alert('输入不能为空！')
            // 给用户输入的内容包装成一个todoObj对象
            const todoObj={id:nanoid(),title:this.title,done:false};
            this.addToDo(todoObj);
            this.title='';
        }
    }
}
</script>

<style scoped>
/*header*/
.todo-header input {
    width: 560px;
    height: 28px;
    font-size: 14px;
    border: 1px solid #ccc;
    border-radius: 4px;
    padding: 4px 7px;
}

.todo-header input:focus {
    outline: none;
    border-color: rgba(82, 168, 236, 0.8);
    box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 8px rgba(82, 168, 236, 0.6);
}
</style>

src/components/MyList.vue

<template>
    <ul class="todo-main">
        <MyItem
             v-for="todoObj in todos" 
             :key="todoObj.id" 
             :todo="todoObj" 
             :checkTodo="checkTodo"
             :deleteTodo="deleteTodo"
        />
    </ul>
</template>

<script>
import MyItem from './MyItem.vue'

export default {
    name: 'MyList',
    props:['todos','checkTodo','deleteTodo'],
    components: { MyItem }
}
</script>

<style scoped>
/*main*/
.todo-main {
    margin-left: 0px;
    border: 1px solid #ddd;
    border-radius: 2px;
    padding: 0px;
}

.todo-empty {
    height: 40px;
    line-height: 40px;
    border: 1px solid #ddd;
    border-radius: 2px;
    padding-left: 5px;
    margin-top: 10px;
}
</style>

src/components/MyItem.vue

<template>
    <li>
        <label>
            <input type="checkbox" :checked="todo.done" @change="handleCheck(todo.id)" />
            <!-- 以下代码也能实现功能，但是不太推荐，因为有点违反规则，因为修改了props，只不过vue没有监测到（vue监测到的情况是对象全部被变化 -->
            <!-- <input type="checkbox" v-model="todo.done"/> -->
            <span>{{ todo.title }}</span>
        </label>
        <button class="btn btn-danger" @click="handleDelete(todo.id)">删除</button>
    </li>
</template>

<script>
export default {
    name: 'MyItem',
    //声明接收todo对象
    props: ['todo', 'checkTodo','deleteTodo'],
    methods: {
        handleCheck(id) {
            // 通知App组件将对应的todo对象的done值取反
            // console.log(id);
            this.checkTodo(id)
        },
        handleDelete(id){
            if(confirm('确定删除吗？')){
                this.deleteTodo(id)
            }
                
        }
    }
}
</script>

<style scoped>
/*item*/
li {
    list-style: none;
    height: 36px;
    line-height: 36px;
    padding: 0 5px;
    border-bottom: 1px solid #ddd;
}

li label {
    float: left;
    cursor: pointer;
}

li label li input {
    vertical-align: middle;
    margin-right: 6px;
    position: relative;
    top: -1px;
}

li button {
    float: right;
    display: none;
    margin-top: 3px;
}

li:before {
    content: initial;
}

li:last-child {
    border-bottom: none;
}

li:hover {
    background-color: #ddd;
}

li:hover button {
    display: block;
}
</style>

src/components/MyFooter.vue 

<template>
    <div class="todo-footer" v-show="total">
        <label>
            <!-- <input type="checkbox" :checked="isAll" @change="checkAll"/> -->
            <input type="checkbox" v-model="isAll"/>
        </label>
        <span>
            <span>已完成{{ doneTotal }}</span> / 全部{{ total }}
        </span>
        <button class="btn btn-danger" @click="clearAll">清除已完成任务</button>
    </div>
</template>

<script>
export default {
    name: 'MyFooter',
    props: ['todos','checkAllTodo','clearAllTodo'],
    computed: {
        total() {
            return this.todos.length
        },
        doneTotal() {
            // 数组.reduce()方法
            // const x = this.todos.reduce((pre, cur) => {
            //     return pre + (cur.done ? 1 : 0)
            // }, 0)
            // return x
            return this.todos.reduce((pre, todo) => pre + (todo.done ? 1 : 0), 0)
        },
        // 计算属性简写版
        // isAll() {
        //     return this.doneTotal === this.total && this.total > 0
        // }

        // 计算属性完整版
        isAll:{
            get(){
                return this.doneTotal === this.total && this.total > 0
            },
            set(value){
                this.checkAllTodo(value);
            }
        }
    },
    // methods:{
    //     checkAll(e){
    //         // console.log(e.target.checked);
    //         this.checkAllTodo(e.target.checked);
    //     }
    // }
    methods:{
        clearAll(){
            this.clearAllTodo()
        }
    }
}
</script>

<style scoped>
/*footer*/
.todo-footer {
    height: 40px;
    line-height: 40px;
    padding-left: 6px;
    margin-top: 5px;
}

.todo-footer label {
    display: inline-block;
    margin-right: 20px;
    cursor: pointer;
}

.todo-footer label input {
    position: relative;
    top: -1px;
    vertical-align: middle;
    margin-right: 5px;
}

.todo-footer button {
    float: right;
    margin-top: 5px;
}
</style>

src/App.vue

<template>
    <div id="root">
        <div class="todo-container">
            <div class="todo-wrap">
                <MyHeader :addToDo="addToDo"/>
                <MyList :todos="todos" :checkTodo="checkTodo" :deleteTodo="deleteTodo"/>
                <MyFooter :todos="todos" :checkAllTodo="checkAllTodo" :clearAllTodo="clearAllTodo"/>
            </div>
        </div>
    </div>
</template>

<script>
import MyHeader from './components/MyHeader'
import MyList from './components/MyList'
import MyFooter from './components/MyFooter'

export default {
    name: 'App',
    data() {
        return {
            todos: [
                { id: '001', title: '抽烟', done: true },
                { id: '002', title: '喝酒', done: false },
                { id: '003', title: '开车', done: true }
            ]
        }
    },
    components: { MyHeader, MyList, MyFooter },
    methods:{
        // 添加一个todo
        addToDo(todoObj){
            this.todos.unshift(todoObj)
        },
        // 勾选or取消勾选一个todo
        checkTodo(id){
            this.todos.forEach((todo)=>{
                if(todo.id===id) todo.done=!todo.done
            })
        },
        // 删除一个todo
        deleteTodo(id){
            // 注意:filter不改变原数组，只是新建一个数组
            this.todos=this.todos.filter((todo)=>{
                return todo.id!==id
            })
        },
        // 全选or取消全选
        checkAllTodo(done){
            this.todos.forEach((todo)=>{
                todo.done=done
            })
        },
        // 清除所有已完成的todo
        clearAllTodo(){
            this.todos=this.todos.filter((todo)=>{
                return !todo.done
            })
        }
    }
}
</script>

<style>
/*base*/
body {
    background: #fff;
}

.btn {
    display: inline-block;
    padding: 4px 12px;
    margin-bottom: 0;
    font-size: 14px;
    line-height: 20px;
    text-align: center;
    vertical-align: middle;
    cursor: pointer;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
    border-radius: 4px;
}

.btn-danger {
    color: #fff;
    background-color: #da4f49;
    border: 1px solid #bd362f;
}

.btn-danger:hover {
    color: #fff;
    background-color: #bd362f;
}

.btn:focus {
    outline: none;
}

.todo-container {
    width: 600px;
    margin: 0 auto;
}

.todo-container .todo-wrap {
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
}
</style>